Well, technically multiclass is always a power hit, since you can't then take a paragon path...and the abilities granted by paragon multiclass are weaker (typically) than paragon powers, plus you lose the paragon class abilities. PLUS the FOUR feats required to do it at all.
That said, it can be pretty effective too. I'm pretty happy with Thorn, for example. Maybe I shouldn't be...a level 30 pure rogue could well be scads better...but I am.
But as I look at warlocks, I think multiclassing is less attractive. Most of what wizards can do, warlocks can do too...so there's not nearly as much to gain from it. I might take Ritual Caster though...just because SO much "utility" magic is now rituals.
Edit - all that said, the ability of a warlock to curse multiple opponents, combined with a wizard's large selection of area blasts...has certain temptations...
That said, it can be pretty effective too. I'm pretty happy with Thorn, for example. Maybe I shouldn't be...a level 30 pure rogue could well be scads better...but I am.
But as I look at warlocks, I think multiclassing is less attractive. Most of what wizards can do, warlocks can do too...so there's not nearly as much to gain from it. I might take Ritual Caster though...just because SO much "utility" magic is now rituals.
Edit - all that said, the ability of a warlock to curse multiple opponents, combined with a wizard's large selection of area blasts...has certain temptations...