Interestingly I've never come across any pure Solaris shops that run ZFS, I suppose because if you're conservative enough only to use Solaris, you're too conservative to trust ZFS.
Also, solaris is probably the most stable OS i've ever worked with.
Agree with you to some extent on stability - I've seen Solaris boxes with a load of 300+ still up and running although unusably slow, where Linux would almost certainly have died from resource starvation. In general use, both Linux and Solaris are pretty damn reliable though.
(This is a question of genuine curiosity. SMF has led to many headaches when I've had to deal with it, simply because it didn't seem to comply with normal conventions like returning nonzero for failure or actually printing what goes wrong to the console.)
EDIT: add trailing parenthesis.
Just kidding.
Call me a BSD bigot (even though I use Linux/OS X at work) but I really fail to see any rational reason to use Solaris at this point.
We have a Solaris database + filestore at work, mostly for Z-raid, but now that FreeBSD has ZFS, when it gets EOL'd (with a vicious grin on my face) it's going to be a BSD box that replaces it.