I got an OpenSolaris CD during the CommunityOne conference and became curious about the content. Instead of trying it out with VMWare,
I decided to evaluate VirtualBox for that purpose and downloaded it during a not so exciting JavaONE's AMD General Session :-).
I was surprised by the size - there are only about 22 MB. The last VMWare upgrade to 6.0.3 was exactly 330 MB.
VirtualBox is very similar to VMWare. It allows you to create an image from a CD, or start an existing one. You can manage and create the virtual drives.
The installation of OpenSolaris was smooth and without problems.
VirtualBox is opensource, and seems to be free. The opensource model could become really important in the future for VM-tools, because of the properietary image format. Right now you have to trust your virtualization vendor - the images are not standardized and not compatible.
I'm not sure about the performance, but OpenSolaris (the CommunityOne edition :-)) runs fast under VirtualBox. So what are the caveats/drawbacks? :-)
NEW: Online Workhop Effective WebApps without Frameworks is also coming to: MUC Airport.