For some all you need is maps. Some want at least maps and minis. Some want maps, minis, and dice. Some want things up to and including full mechanics, rules, and system integration along with full automation so all you have to do is click a button and the computer will spit out the results.
Keep in mind the question: what is the bare minimum for a VTT?
Where do you fall on this spectrum?
Supported on Mac, Win, Android, iOS.
Map and tokens.
Supports square grid, hex grid, ungridded, and isomorphic (long axis horizonal diamond/lozenge grid)
supports 15° rotation increments
supports both metric and English Traditional Measure; Japanese traditional measures a bonus.
Ideally, the method of grid setting being like the one in GTove, at least as an option. (It's set a pin in one vertice, set a second in a vertice down and right. Since GTove is free, you can check it out at
gTove. This system allows it to easily adapt to not-quite even hexgrids and squaregrids easily.
As for dice, I don't like them on the surface, but love having them in chat. Also, support for user defined dice such as those in 2d20system and FFG NDS games.
I don't care about minis as long as token support is robust, and allows multi-grid figures in non-square as well as square/round.