My brother has a G30, and I have a G21. I haven't had much range time with the 30, but I feel my 21 shoots just as well as any of my 1911's.
The 30 has the "hump" in a different spot than the 21. They will both feel differently in your hand. I like the way my bro's 30 feels, but I like full size guns.
Remember, the 45's have octagonal rifling compared to the hexagonal rifling of all the other Glocks. Many 45 glockers consider the 30 to be the most accurate glock. I shoot my 21 better than I shoot my brother's 30, though.
The funny thing is, I'm a 1911 shooter by birth, and there was no way I thought I could like the feel of a Glock (I have small hands). I'll probably get a 30 for myself in the future for CCW, because if anything happens to one of my 1911's, it makes me want to cry. The glocks, OTOH, I could through across the parking lot and not really care. I'll just get another.