I should have mentioned that I have one form to handle a large transaction. It contains 9 tabs, all have mostly just grids but one tab has about 30-40 controls. We use a number of custom controls for DateTime and Number fields in addition to custom grids. It used to take about 10-15 seconds to show the form in the designer (just double-clicking the form), it now takes about 3 or 4 seconds. While my wife thinks I'm inpatient because I told her the 15 seconds was "too long", it really is a *long* time to wait for something so simple as tweaking a UI control. It also makes running the program/debugging more difficult because it takes over a minute to get to the point where the form is loaded in the correct state to test (mostly a lot of searches and what-not to get there).
If you have large forms or large projects, a faster machine is well worth the investment. I used to find myself distracted since, as I said, it took over a minute to get to the point where I could prep the form for debugging. I'd check/send an email, etc. while waiting, but it just spread out the time to debug. Not a good idea...
Of course, if MS ever puts back in the edit-and-continue (with the changes), this may help stop this. It's the one thing I miss about VB6 and prior.
-Nerseus