Well, I think I should be able to supply you with a good answer - as an architect who's currently building my own gallery and has designed walls for the guggenheim. Generally speaking, you DEFINITELY want some backing behind the drywall. Use the thickest drywall you can possibly deal with - if you have a long run of wall it will pay off. I'm using 5/8" type X (since yours is not a fire-separation wall you don't need to use X) but this is the THINNEST that I would use. The drywall alone won't REALLY cut it - unless you're hanging really light stuff and you're into patching.

But anyway - most people seem to want to use 3/4" CDX or else 1/2" baltic birch ply (stronger - and not really more expensive actually!). You can either overlay on top of the studs which is EXPENSIVE since you'll have to cover the ENTIRE wall - or else block in between studs only at hanging height. What would be cheaper still, and better - if you're hanging conventional works at a standardized height - is to use 2x12s blocked in between studs at a height that will work for you. If you choose to hang ply or 2Xs between studs - you'll need to screw 2x2s in so the backing material can be screwed into something. (and yes, use screws!! I like deck screws). So the 2x2s will have to be offset by the thickness of the backer.

Of UTMOST importance is going to be how good your framing is. If it's not dead-on, it will show. This also applies to your plaster work. Do the drywall yourself - but find someone to tape and mud it and DEFINITELY skim-coat the thing. It will really pay off.