I don't see it listed on the steam page which kinda blows. How do you play 4 player co-op then? Or is the co-op online only? 
These types of games are good with the 360 controller, if you have the wireless receiver.

I don't think the game supports it but the co-op is online only with a SP tutorial and the game is great with the mouse.

Can confirm 360 pad works. Xpadder or other "make my 360 pad not a pile of crap" tools don't seem to be required.
 
Mega edit (from the Penny Arcade forums):
 

Enter these commands at the console:

exec 360controller_PC
bind "JOY4" "asw_InvLast"

The default controls are:

Left stick – move
Right stick – aim
Right trigger – fire
Left trigger – alt fire
Right bumper – reload
Left bumper – use offhand item
A – roll
B – melee
X – use
Y – switch weapons
Back – Show map/objectives

How does the hacking consoles work as a Tech when you're on controller?
 
Also knowing that the screen pans however which far you're pointing the mouse away from your guy, I wonder if the controller automatically pans to the farthest point on a controller or would it be based on how much you tilt the stick?
 
I'm a big twin stick shooter guy before so I wanted controller support outright, but having played it a bunch on mouse keyboard I kept wondering how they could implement the controller in it. That said, there is no doubt that swinging your aim arcs in this game and switching sides is best done by stick and not by moving your mouse in relative location to your character. (Because if your character was just even a centimeter off then you could be aiming and turning the completely opposite way on mouse and keyboard.)

This thread has full instructions and tips on using a 360 controller (hint: it's very easy to do since Valve has basically already done all of the work to support it):
 
http://forums.steampowered.com/forums/showthread.php?t=1370149
 
I've tested what's in that thread and it works perfectly well.  I, personally, still prefer the feel of using a mouse and keyboard though--aiming is faster, as usual.
 
P.S. @Kintaro:  The hacking minigame looks the same, but you have a selection cursor that you can move over the pipe sections to activate them.  It's very nearly as effective as using a mouse.  I haven't tried the other minigame, so I can't comment on it.

"Can confirm 360 pad works. Xpadder or other "make my 360 pad not a pile of crap" tools don't seem to be required.
 
Mega edit (from the Penny Arcade forums):
 

Enter these commands at the console:

exec 360controller_PC
bind "JOY4" "asw_InvLast"

The default controls are:

Left stick – move
Right stick – aim
Right trigger – fire
Left trigger – alt fire
Right bumper – reload
Left bumper – use offhand item
A – roll
B – melee
X – use
Y – switch weapons
Back – Show map/objectives

 You'll have to enable the developer console in the keyboard/mouse options and hit ~ to bring it up. This works really well. Some of the tutorial popups are fucked up but who cares. "