This is good.. I've always loved the idea of updates being thoroughly tested before released.. A quarterly schedule will give them time for stable releases.. Moreover important from the fact that solaris ( also opensolaris ) is largely non existent for desktop users and even in the server and security market they've stiff competition..
I rather run FreeBSD on my home server. I don't really like Solaris. Probably because I've been using UNIX-like OSes in so long I'm not used to real UNIX OSes. I don't know.
However, I think software updates should happen immediately instead of every quarter. I don't like the idea of waiting every 3 months for security patches.