My answers are identical to RPMillers for the most part.
Couple things I would like to add:
- What is important for me in a VT is the ability to improvise on the spot. You know players as well as I do - you have no idea where they will be going today. It is important for a GM to be able to do the same things he can do with a rubber battlemat and be able to draw stuff on the fly quickly. Maptool is able to do this very well and I use it every game. These on the fly drawingas can be as simple as using a dry erase or as advanced as using textures to draw with.
- This reminds me of a contest we had at RPTools.net to see who could make the fastest map on the spot. It can be found here: http://forums.rptools.net/viewtopic.php?t=2624
- The greatest thing about a VT battlemat versus a rubber battlemat is that there is no limit to the size of the battlemat (at least in Maptool anyway). I have had players who never bought the Longshot feat (D&D3.5) previous to Maptool because they knew that encounters never get that big. Now with Maptool, I have players shooting 1000' away (200 cells) and enjoying every minute of it. No rubber battlemat is going to be THAT big!