I'm writing a feature screenplay currently, but it is not a comedy. Do you think if I posted it on here people would still read / critique it? Or should I stick to just comedy.

Write whatever genre you feel comfortable with.

Post only a short part of your script, the first 10 pages max, in the Critique forum.
I'm sure it'll still be reviewed, even if it's not comedy.

http://www.gitsclub.proboards.com/

You might want to try this place.

They're Americans so go gently with them - no sudden irony.
It also means you'll get A LOT of structure/format comments.
But they're good people.
It's a fledgling board so you're more likely to get a read and a comment.
Most of the peer review sites ( Triggerstreet, Zoetrope) are MASSIVE and usually require you to review lots of SP's first - which can become a hobby in itself and a terrible waste of time.
It's on offshoot of Go Into The Story a well respected wannabe screenwriters blog and worth checking out.

You could try posting here, but the fact that it's a full SP and not comedy could limit your chances.
But you never know - there are quite a few screenwriters lurking around and you might get lucky.