It made the prequel trilogy watchable to me again. I really hated the prequels (other than episode 3) before this. Poorly done fan edits can be very jarring with their cuts, but Hal9000 does a very professional job - the only time it is noticeable is when he re-inserts a deleted scene of inferior video quality to help the flow of the movie.
Ep. 1 had some very annoying characters and the Hal9000 edit makes one of them more like an everyman alien who gets caught up in things and just makes a few goofy mistakes while in the original his character made me want to gouge my eyes out with his constant ineptness and poor attempts at humor. The kid in episode 1 was also made much more tolerable without annoying yippie, whining, and made the kid more pro-active. The pacing at the beginning was much better by cutting out an unnecessary side trip and getting rid of crap that doesn't belong in a Star Wars movie - OH NO TAXATION! Also, it makes the minions of the trade federation more of a threat - they originally had cringy (roger roger) dialogue that made them seem like a joke.
Ep. 2 and 3 were also much improved. After the edits episode 2 is still not that great of movie, but the original version was nearly unwatchable. The flow is much better, the main character is no longer a whiny annoying teen and the romance is more believable/less sappy. It also got rid of one of the most ridiculous action scenes ever thank goodness and a part that felt like a frigging video game sequence. It is still worth watching as a setup for episode 3 (which is a very good film) and the Hal9000 version at least makes Episode 2 decent.
As for episode 3, I always enjoyed the original and feel like people shouldn't skip it even if they don't watch the other prequel movies. However, the original version did have pacing issues, some horrible dialogue, and some important characters had little to do in the film and others acted out of character. The Hal9000 edit fixes allot of that and makes it into a really entertaining film, although there is still the infamous NOOO!!!!! scene in it, lol. Hal9000 felt that scene was important and couldn't find a way to edit it better and not make it feel jarring. I really liked how the Hal9000 edit gave Padme something to actually do in the film other than standing around crying, and I liked how it made Anakin's struggle more internalized and not focused on only a single topic.