The installation was fast and easy, comparable to the installation of Ubuntu.
OpenSolaris seems to have big problems in terms of wireless LAN. I am using a WPA/WPA2 encrypted wireless LAN, and it asked to me to enter my passphrase. I entered it, and nothing happened. I was able to get wireless working via commandline, but this lead me to the problem that domain names were not resolved. I could solve this, too. But none of this was permanently, and it should work the graphical way or tell me it does not work. Maybe this whole thing happened because I have a space in the name of my Wi-Fi network.
Another problem is suspend/resume, which is not yet working for most laptops; whereas recent Linux distributions support suspend/resume out-of-the-box.
OpenSolaris ships non-free components, e.g. NVIDIA display drivers, or Java 6 Update 10. Hopefully, there will be an option in future to install it without this stuff.
Talking about the desktop, there is GNOME 2.24 with a custom theme. In my opinion, the theme looks quite good, although I do not like the colours of the minimize,maximize,close buttons of the windows sometimes.
One feature introduced with this release is Time Slider. Time slider worked very well, although for reasons I do not know, I do not really like it. The integration with nautilus is good, but I would still like to see an interface using a calender widget instead of this slider. I remember that the slider sometimes did not work as I expected, e.g. it jumped from left to right.
The package management is interesting, but it is to hard to use in my opinion. Debian and derived distributions provide far better package managment in my opinion. Especially the graphical part needs a lot of work in order to compete with Debian.
The overall speed was quiet good, and memory usage was 512MB. There is one problem with measuring memory consumption in gnome-system-monitor: I installed netbeans 6.5 and started it, and gnome-system-monitor showed a memory usage of around 20MB, while the program used more than 200MB (according to top).
All in all, OpenSolaris gets closer to modern Linux distributions like Fedora 10 or Ubuntu 8.10, but it is not there yet. But with improvements in the area of Wi-Fi and Suspend/Resume, future releases of OpenSolaris might become a good alternative to Linux distributions, at least if you do not really care about the ideas of free software.