On the upside, it's not a bad film. It depends what you want out of your Trek, of course, but from where I'm sitting it had fun continuity references, an intriguing bad guy, and a cool space battle.
On the downside, it's The Wrath Of Khan. Now, I'd heard this said before I went to see it, but I hadn't realised quite how true it was. The traitorous crewmember, the evil alter ego, the battle of wits inside a nebula, the climactic death of a main character (with an obvious "ah, but he's not really dead, d'you see?" in both cases)...it's all there.
There's a joke to be made about whether Nemesis is itself the evil twin of The Wrath Of Khan, but I can't quite find it...