They're not as terrible as people are making them out to be. Granted, Lucas got a bit carried away by his FX, and the story lost a little of the joy it had the first time out. But overall, it still adds up to make a fun story. If you go into it expecting movie fun in the spirit of an old time matinee, you'll be satisfied. If you go in expecting deep, grand movie making in the tradition of The Godfather, you'll be disappointed.
Okay, a lot of the acting is pretty bad. But a lot of the acting was pretty bad in the original three, as well (even you die-hards know it's true, if you're really honest with yourselves ). Episodes I - III are still fun. And, I admit, I cried like a baby at the end of III (yes, yes, feel free to ridicule me, now ). I think they're worth the time. Don't go into them expecting Great Theater, take them for what they are, and you'll have a good time.
There. That's my $1.75 (inflation) on the matter.