Me and a friend marathoned through GT last year - definitely have to agree with those who see it as a step down. Some wonderful ideas at points, but very few of them are realised well and the pacing and tone are all over the place - particularly noticeable with the slow-paced more comedic Black Star Dragon Ball arc leading into slow-paced but more Z-like Baby arc, then following those up with the super-rushed Super-17 arc! The focus staying on Goku so much is pretty problematic, too, as is his completely inconsistant power scaling - turning him into a child should have been used as a way of keeping him out of the picture and letting the new generation of characters shine, by scaling his powers back to early Dragon Ball levels in accordance with his age. By all means, involve him with the adventures, but give another character the chance to be the hero for a change!
Love Dragon Ball and Z in spite of all the filler, though I do find the Red Ribbon arc of Dragon Ball a bit of a slog - I've heard it's much more streamlined in the manga, so maybe I'll try to read through at some point and see if it changes my opinion on it. In my opinion the high point of the series as a whole is the period from the Demon King Piccolo's appearence through to the defeat of Freeza - the way the tone and the art style develops through this period combine to form what I've come to think of as the quintessential Dragon Ball look and feel. However, I'm also a big fan of the 22nd Tenkaichi Budokai and the Cyborgs/Cell arcs, and though they're not quite in my absolute top-rated section of the series, were I to marathon the series again I'd probably use these as my starting and finishing points.
Still not seen Battle of Gods, but I've heard good things - with Resurrection "F" on the near horizon maybe now is a good time to catch up. Since these new films are supposed to be within the main continuity (unlike the previous movies - Return My Gohan excepted if you're following the anime's additions), I wonder if they'll set any after Goku begins training Oob, or if they're holding off to avoid explicitly kicking GT out of the animated continuity?