Re: Roll20
I ran a campaign on it, and I think it's pretty slick. The ads might be annoying for some, but they never bothered me too much. If you get a paid account you can get rid of them, but that's your call.
The dice roller/character pages/and maps are what makes it great. You can put all sorts of images and tokens into your own personal library to pull out when you need it. The map also has Fog of War, which can be a godsend depending on how you play. You can also set up separate pages (Floor 1, Floor 2, Basement, etc.) for the players to adventure on. You can also whisper and send secret messages easily, if that is something you do in your campaigns.
The one thing I didn't toy with too much was macros. You could set up pregenerated die rolls (Attack, Search, etc.) and you just hit a button and it rolls them for you. If you get fancy, you can even set up 'Roll STR+Climb for Climbing skill check'.
It has its own in-house video/audio, but when I first used roll20 it was spotty. Granted, that was when it first came out, I just kept using Skype since then. You can also launch it in Google Hangouts, which is a much more solid platform for video and sharing docs.
On the campaign page you can set up threads and have blurbs about the game. You can also set when the next game will be played, and it will track the time until then.
Overall, I thought it was a great leap in the virtual tabletop, and since I've been forced to turn online to play my games, it was a great tool.