When you drag corpses to it, you hear a noise, the freezer glows a bit and a +1 flies out of it and into the air for your viewing goodness. [grin] It gives you a bit of a reward, I suppose.
Some screenshots to manhandle:
The first screenshot shows freezing in action (and lord, that sprite sucks) -- the +1 and the new status screen. I haven't decided if it's a toggle yet, but at the moment you hold down the "I" key to bring it up.
The second screenshot is a hilarious bug I found when I was trying to draw nonexistent freezer sprites. It would be pretty awesome to have a game in this perspective, though!
Also, in combos: Every kill past your 10th in a combo string rewards you with 10HP. It's a great way to survive survival mode, by rationing out your shots to gain health from your enemies. [grin]