Man, I thought the dub was excellent. It might grow on you later though as certain new characters get involved and others grow up.
As for the show itself, it's a very mixed bag at first. 2 and 3 are decent, 5 is the first really good story in the series and is the point where, to my mind, the real journey begins. Also be prepared for the fourth episode, which for some reason is badly produced compared to all of the others and has an impossibly durab plot. It's apparently the only episode with a guest director (Osamu Kobayashi), so make of that what you will. And if you hate fanservice, episode 6 will be the bane of your existence. 4 and 6 I'll probably never watch again.
Starting with 7, however, it gets serious about what it's doing and doesn't stop delivering. Early in the series you think it's all just eccentric and weird for its own sake, but when the big action starts Gainax's excesses become the series' biggest asset. The animation style commanRAB attention, and the scale of battle is ever-increasing. GL has its flaws but if I had to pick a single trait to describe it, it would be arabition. It's very arabitious compared to the classics of the genre, and frankly it makes other offerings in the 00 decade look absolutely terrible by way of comparison. Gravion, Godannar...bah. GL has some fanservice but unlike certain other titles, it doesn't feel like a giant excuse for it. Its ultimate plot is also a surprise.
Incidentally, believe it or not, there are some genuinely enjoyable characters in here along with all the action. That's spoiler territory so I won't go there, but Simon in particular grows a lot. If nothing else, he's worth sticking around for.