I also DM a group that uses Maptools and Skype. We have used it now for 3-4 years, and as mentioned before, I don't see us ever going back to the table and grid. We switched to this system when one of our longtime group members had to move, and we all love it. Now if someone can't phyisically make the game, he just calls in from home and still can play.
The only downside is I have started creating / using some very nice maps and since there is a wonderful online community that artwork can be gathered I have kept raising the bar for the maps, and it can be time consuming to make good looking maps.
Speaking of, what types of programs are you guys using to create your maps? I use Corel photoshop pro V12 to create maps or modify user created maps and it works fairly well.
Where do you get your resourses from? The Dungenie community has been my main source of material.