Ideas: A variety of suggestions

[Paragonville]

So far, Rimworld is pretty darn awesome.  I like how you used Prison Architect's general appearance for it, and I'd honestly suggest pulling even more stuff from that game when it comes to infrastructure.

Anyways, what Rimworld needs is to be -slower- with the events being thrown at us.  I've had the game for a day, and my colony has one hundred raiders buried outside, with no way to reclaim said land.  There's never enough time to actually fix things completely attack after attack.  Half of my map is covered in blood, and every five minutes a dry thunderstorm hits and pummels me. 

Allow for actual immigrants to show up already wanting to join the colony.  Unless I've missed it, you can only hope to capture a raider with half-decent skillsets, buy a slave, or arrest some passerby.  When the comm-system is installed, how about it give out a signal that a new colony has been built, and that people should totally drop in to join the thunderstorm love party.

More stuff to do.  I've already reached this point where I honestly feel that I've seen it all.  Which I have, this is just an Alpha.  Here's a couple ideas:

Robots: You should totally get to make these suckers.  Build a machine shop, and have your resident mechanists build some cool robots that do simple tasks.  Maybe you could even make them go haywire and do strange things, or just become murderous.  (Please make that a very rare occurrence if you do, I already have raiders attacking every five minutes and psychotic muffalos beating my doors down.

Varying quality of auto-turrets: Face it, the current auto-turret does more damage to the player than it does to the raiders.  They are fragile, they do little damage, and the explosion they make is a bit overkill.

Showers: Ain't nobody want to see that blood on you.

More ways to prepare food, the ability to harvest animals for food.

Less raiders, more interesting dangers: How about a spooky fog-monster sort of "enemy" that lurks about outside or in caves at night occasionally in unlit areas.

A landing pad for visiting ships.

The ability to recycle slag debris and turn it into small quantities of metal.  I have a mountain of slag taking up my build space.

Corpse cremation.  Maybe even a Soylent Green method in the event your colony isn't very moral.

Morality system: Evil/sadistic colonists can thrive in a colony full of slaves, cannibalism, and other fun evil things.  Instead of raiders as often, how about... space cops!  Bounty hunters.

Windows!  Why can't I have a proper wall with windows to shoot out of?  More protection, especially if you guys intend to keep sending entire legions of raiders after me.  Really, you'd think they'd get the idea after seeing the twenty or so giblet cages I have set up.

[Semmy]

So far, Rimworld is pretty darn awesome.  I like how you used Prison Architect's general appearance for it, and I'd honestly suggest pulling even more stuff from that game when it comes to infrastructure.

Anyways, what Rimworld needs is to be -slower- with the events being thrown at us.  I've had the game for a day, and my colony has one hundred raiders buried outside, with no way to reclaim said land.  There's never enough time to actually fix things completely attack after attack.  Half of my map is covered in blood, and every five minutes a dry thunderstorm hits and pummels me. 
I personally love the fast pace of the game lets me stay on edge. In the future phoebe friendly will be for the players who want to take it easy (-:

Allow for actual immigrants to show up already wanting to join the colony.  Unless I've missed it, you can only hope to capture a raider with half-decent skillsets, buy a slave, or arrest some passerby.  When the comm-system is installed, how about it give out a signal that a new colony has been built, and that people should totally drop in to join the thunderstorm love party.

More stuff to do.  I've already reached this point where I honestly feel that I've seen it all.  Which I have, this is just an Alpha.  Here's a couple ideas:
It actually is pre-alpha so don't worry it will happen d-;

Robots: You should totally get to make these suckers.  Build a machine shop, and have your resident mechanists build some cool robots that do simple tasks.  Maybe you could even make them go haywire and do strange things, or just become murderous.  (Please make that a very rare occurrence if you do, I already have raiders attacking every five minutes and psychotic muffalos beating my doors down.

Varying quality of auto-turrets: Face it, the current auto-turret does more damage to the player than it does to the raiders.  They are fragile, they do little damage, and the explosion they make is a bit overkill.

Showers: Ain't nobody want to see that blood on you.
Showers nice but where is the water coming from?

More ways to prepare food, the ability to harvest animals for food.
Being worked on. Last time i saw high on tynan's todo list

Less raiders, more interesting dangers: How about a spooky fog-monster sort of "enemy" that lurks about outside or in caves at night occasionally in unlit areas.
There is a topic just for this go look (-: http://ludeon.com/forums/index.php?topic=38.0

A landing pad for visiting ships.
Has been discussed and ships wont land. Takes the endgame goal to create your ship to get off the planet away.

The ability to recycle slag debris and turn it into small quantities of metal.  I have a mountain of slag taking up my build space.
YES SO MUCH WANT THIS. atmossmashers rock.

Corpse cremation.  Maybe even a Soylent Green method in the event your colony isn't very moral.
Also beeen suggested. For now use molotovs or frags

Morality system: Evil/sadistic colonists can thrive in a colony full of slaves, cannibalism, and other fun evil things.  Instead of raiders as often, how about... space cops!  Bounty hunters.

Windows!  Why can't I have a proper wall with windows to shoot out of?  More protection, especially if you guys intend to keep sending entire legions of raiders after me.  Really, you'd think they'd get the idea after seeing the twenty or so giblet cages I have set up.
Why would you make a easy to go entry for those raiders. Let them stay in the dark and fear the world

[Galileus]

As for faster immigration, I would argue the very other way around. It's already too fast. It's common you get the passer-by, then two slaves from orbit, then a raider convert... You end up with Guy1, Guy2 and so on, instead of these colonists you're supposed to know by name and remember.

[Paragonville]

The addition of a multi-level map similar to Dwarf Fortress would be cool.  What if I want to build my base below ground and live like the mole people!

Have a sand bag perimeter on the surface of course with some auto-turrets and a weapon shed.

[Galileus]

The addition of a multi-level map similar to Dwarf Fortress would be cool.  What if I want to build my base below ground and live like the mole people!

Have a sand bag perimeter on the surface of course with some auto-turrets and a weapon shed.

Not going to happen.

[Paragonville]

Update:

Possible lockdown mode, which forces all colonists to drop what they're doing and run inside?

Prevents colonists from having to remain in military mode for the entirety of a raider attack.