I just finished installing Solaris Express Developer Edition 9/07 on VMWare Fusion 1.1 on my MacBook Pro.
Well, I don't know what to say. I just can't think of any complaints. The install was simple and painless, I was able to install the VMWare Fusion tools without a hitch , networking Just Works, Firefox Just Works, NetBeans 5.5 Just Works, including Java DB is Just There and Works. File sharing works. Navigation between Solaris and Mac applications works.
I have tried many early installs of Solaris, and I have never been in this baffling situation of having absolutely nothing to complain about (and believe me, I don't keep my mouth shut).
I can go to full screen mode, and it stays in full screen even when I suspend and resume (unlike Ubuntu under Fusion).
I'm downloading Ant and am going to give a NetBeans build a go. We'll see how it goes; I am getting myself ready to shift over to a real developer's platform, that actually has Java 6 and a working version of Open Office and top-level AMP and PostgreSQL support. I'll keep the Mac around for consumer-oriented stuff like playing Rhapsody, but I think in general it's going to start moving to the background of my day...
One other nice thing about running Solaris in Fusion on the Mac -- I can suspend my computer. If you have Solaris installed natively, no suspend. They're working on it, but meanwhile, this is a pretty good workaround.
 Well, just one hitch, per Felipe's blog. After installing and you reboot, VMWare thinks you are booting a 64 bit OS in a 32 bit guest. You have to do add the following to the .vmx configuration file:
monitor_control.disable_longmode = 1
After you successfully boot this way, VMWare recommends you remove this line as it can confuse some applications.