Given that OpenSolaris is derived from Solaris, one of the premiere server OS' for a substantial period of time, and that server OS' absolutely need stable network management, I find it odd that OpenSolaris would have this problem. This is a seasoned OS by a seasoned team - so seasoned that Solaris had IPv6 support before any other OS, Linux included - making problems with the network stack and network administration tools very difficult to understand.
The problems with making Solaris a desktop OS in addition to a server OS are more understandable. It's a very different world. The sorts of power management issues that x86 Solaris running on mid-sized iron faced are not the same as the sorts of power management issues a laptop contends with. I would still expect better QA from Sun, they are not novices, but allowances can be made.
The disk partitioning issue in Solaris is one I'll never understand. BSD doesn't use the Microsoft partition table, it uses its own system, so there is no obvious reason why one pointer to its system should be any more or less valid than any other pointer. Hiding details also makes no sense, as it makes it much harder to use tools outside of the OS, as you can't equate the label you use inside the OS with the label the system is going to use outside the OS.
Still, it sounds as though Sun has steadily worked its way through the issues list and has mastered a whole new domain - something very few OS vendors can boast.