This is probably the biggest buff for wizards. Now being a specialist doesn't cut you off from schools! While adventuring, you probably still won't make a habit of using opposition schools; the opportunity cost of losing two spell slots is too high. But the ability to use something like, say, Contingency during days off is great. Verdict: Excellent!
Saph, you didn't mention something that makes Specialist wizards even better. They are no longer prohibited from using wands and scrolls of their opposition schools. Hell, they can even craft those items, although at a -4 penalty. And if your party has two wizards with different opposition schools that's even better.