I must agree. I have been a pretty heavy solaris user since 5.8. I was not at all happy with 5.9 but 5.10....... WOW.
I am typing to you from my ultra60 Workstation. I have been using 10 on the desktop since it dropped. Its great.
Finaly a decent patch management method!!!
Performance of 10, in my opinion, is not at all bad. Very close to what I expect out of freebsd, and I get the added scaleability of Solaris.
It has an excelent desktop (Java Desktop aka Gnome) and all the tools I normaly install on my own.
When used with Sparc hardware you gain use of a large number of hardware specific commands. It has the best drive management systems I have seen standard in an OS. In my mind, it rivals veritas.
(I have also been testing ZFS.... and have nothing but good things to say.)
The only thing that needs to be improved are the development tools. Sun Studio11 needs to be worked on. It needs to have more compatable libraries with GCC and other GNU compilers. That is still holding back Solaris adoption a good bit.
Overall, Solaris10 is one of the best *nixs out there.