Solaris zones are awful, and a good example of where Linux is far superior to Solaris. The creators of Zones seemed to have user-mode-Linux as their model, and it shares most of the annoyances of that too. It's not virtualization, and it's not a jail - it's a middle ground which is good for neither.
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.
Whats so bad about zones?
It's clear that they are no virtualization. As you said it's a middleground, more capable as jails but not virtual, which is fine if you don't need it?
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.