Vincearlia,
I have a very similar setup to what you're talking about. I can run 800+ part assemblies no prob in lightweight mode. The only limitation I've had is when I have those huge assemblies open with multiple (detailed) automotive engines throughout different configurations of the main assembly, my computer doesn't really know how to handle that too well. After running Anna Wood's benchmark part, I had a rebuild time of 120 secs. It's not great compared to better PCs...but not that bad either...there are other way worse systems out there. Overall, I would give it a "C" for solidworks use...but an "A" for doing what I ask from it because solidworks is not what I originally bought it for.
Also, if you have a 3DConnexion device, it translates, rotates, and zooms smoothly within those large assemblies...which blows away some of the guys I work with
Earlier this year, I ran out of space on my Windows partition (originally 30 or 40GB) because of the solidworks stuff. There's a new (FREE!!!) program out called CampTune which allows you to re-size your windows partition pretty easily. It just takes a while to complete. The amount of space required for your partition is up to you. Now I have 100GB of the hard drive dedicated for my windows partition....and whenever I finish an assembly, I store the files on a Linksys NAS200, transfer files over using Beyond Compare, then delete the assembly from my Apple. Overall, I've been pretty happy with the set-up.
Only run solidworks through Bootcamp. Parallels and the other one are terrible to use with solidworks...I've tried them both. When you install the Bootcamp partition, you're Apple becomes a PC, which freaks people out. So really any application/document you can see/install on a PC, you can install it on that side of the partition. In order to switch back to OS, you'd have to restart your computer and select OS X from the start-up screen...which takes maybe 2 minutes to do.
Be careful though, your Windows partition is vulnerable to viruses like any other PC....it would only affect the Windows partition, but void the warranty on your Apple.