I've switched my 2008 MacBook Pro to SSD, and love the speed increase.
I'm now keen to do the same on my 2007 Mac Pro desktop. I've currently got 1Tb + 2*500Gb disks installed. My strategy is to go for a startup disk of about 128Gb, with the 'bare minimum' stored on it, then leave the rest of my data on the traditional hard disks.
So, if I'm mostly doing Java (Eclipse) development, plus a couple of VMWare Fusion Windows installations (used for testing), what is it most worth putting on the SSD? And what shall I just leave on the magnetic disks.
My gut feeling is that it's worth putting my Java IDE plus sources on SSD, since in compilation there's lots of disk access. The Fusion VMs can probably sit on Magnetic disks, I don't mind a penalty starting them up: it's just once per week or so.