SSD are huge in my mind, I can't see myself going back to a HDD based computer for my main Mac. (so in my laptop, desktops can stay HDD, so thats where I want big storage, for me at least...unless I get a Mac with two slots for HDD/SDD)
I think desktops get the most benefit. Im getting the revodrive for my desktop. Using PCI slot gets you past the stupid bottleneck of SATA. than you get a 2nd 10k rpm HDD and your flying. USB 3.0 is also there for quick backups.