I just ran a dungeon crawl using Savage Worlds Fantasy Companion
3 of the 5 players showed up and we played. The three players used the other two characters (the Halfling burglar and the Half-orc fighter who is also a pacifist and a potential berserker) collectively.
The players managed to clear the sewers, beneath the town of Socanth, of the horrors and pests therein, and thereby brought relative peace and prosperity back to the town. I won't go into more details in case I want to run it again. All the players had at least read the quick start rules, so I didn't have to use a lot of time teaching everything.
I think the highlight of the night was the wizard attacking with her staff and rolling 23 on an exploding d4.
We played for almost 3 hours and had no problems aside from one player, who once, randomly got disconnected (it probably wasn't a roll20 problem though) but he was back in less than a minute.
Now on to my thoughts on the VTT:
Macros: Before the game started I had crafted many macros that did many things, but quickly stopped using all my complicated ones. For most of the session I was using macros that were variations on /roll 1dX! and was doing the math in head and calling the results, like I do in "Face To Face" gaming.
IMHO Roll20 doesn't need an overly complicated macro system, what it has now I found sufficient, the one thing I do wish it had was a way to roll 2 or more Dice at one time and NOT add them together, and then have the result appear on the same line (unless it already has one, and I can't figure out how to it).
I would like output to look like this: (3)=3 text, (5)=5 more text.
I have now used roll20 from both sides, once as a player and tonight as a GM I find roll20 very useful. For over a year I haven't been able to find anyone in town to play savage worlds, using roll20 I have managed to get two games in less than a week.