The biggest problem with drum editing is the simple fact that drums are usually constantly making noise. Think about it for a second. If you think of just a kick and snare beat with no cymbals or hihats, there is silence. It's very easy to edit in between the silence. Moving a kick or snare drum in this case is easy. Now, let's add a closed hihat. It's still possible to edit. However, if you move the kick, you also move that hihat. So maybe the hihat was just fine. Well now it isn't!! The hihat is ruined or is going to need some special treatment. This problem gets even worse when ride cymbals (that ring out for a long time) or open hihats are used. Basically any stuff this is ringing out (but also decaying) will have to be cut and moved. This is VERY tough to do most of the time, but it really depends on the tracks that have been given to you.
Most big boys that edit drums extensively, will do 5 or 10 takes of the drums. Only the really good takes are kept. From there, if there is a problem with the second verse, you have 5-10 different verses to look at. If a click track was used, it's no big deal at all slap in Verse #2 from take #4. With this system, you not really adding or subtracting time from a part. You are pasting a different take in. In this method you do not have to worry about shifting other parts of the drum kit. It still can be a big hassle getting the drums to fit properly just because the drummer have used a closed hihat on Take#1 but a slightly open hihat on Take#3.
Basically, drum editing can improve takes, but it's not always THAT quick. You are much better just getting a great take from the beginning. It will just feel better!! When I was down at the Michael Wagener Workshop, the drummer (who was damn good!) played a take. He liked it all except for just one thing. He asked Wagener if he could fix that one thing. Without even a moments hesitation, like a well trained spy agent, Wagener insisted, “NO!! I can't do anything to your drums. That's your job!”. The drummer than said, “You mean with all this SHIT you have laying around here, you can't even fix a drum part!!???”. (Wagener did have about as much gear as one could imagine). The point is simple. Wagener knew that the drummer was more than capable of playing a great take and didn't need to be edited. He know the results of editing would not be satisfactory. He also knew it would waste a lot of time that could be used to improve other things.