Xcode runs much faster now. Its still going to be the slowest (and largest) application you'll load (besides iTunes). But, it doesn't feel as heavy anymore.
Builds are much faster for me; one project used to take > 2m30s to build and now builds in just over 1m (between getting an SSD and switching from gcc-4.2 to clang).
I wasn't quite sure what you were asking, so I went with a generalized response. If you want more info (Xbench, etc), please ask (here, or in email if you prefer). I figured since you were asking about Xcode and the SSD, rather than the screen size specifically, I might be able to answer your questions.
BTW have you tried Windows in a VM on it?
Only briefly. I spend more time running a VM of Slackware. I don't notice any slowdown in using it and it does seem faster than before. But, I haven't done any benchmarking (since I don't have a "before" to compare it to).