Guy,
I followed your link, and read your comments on KS re what you are looking for in a VTT. I have zero stake in roll20 except as a (free!) satisfied customer, but I want to point out it meets many of your requirements in a system that is working and available right now. Look, here we are playing
Curse of Katiki-Mu!!
1. roll20 is free, for the players and the GM.
2. roll20 is browser-based and cross-platform (although doesn't seem to work on my ipad)
3. roll20 has fantastic support for hex-grids.
- Figures snap to the middle of hexes, hex facing is easy to change and snaps.
- You can easily indicate the exact path of hexes your figure will take. Useful in complex battles
- Line of sight tool (I suppose that's not hex-specific, but we use it all the time)
4. it can handle multi-hex figures. You use the alt key to move, rotate, and resize
There is also loads of support for RPG mechanics of all sorts, it's very popular for that reason.
What roll20 surprisingly
doesn't have is any support from SJGames, for GURPS or TFT. For many other games there are official character sheets. It seems like roll20 might be very happy to work with SJGames to organically develop this simple form of support? From there, who knows....? :)