I voted for none but it depends a little. For outdoor use I don't see any need for a grid at all. With hex I always thought it was more for convenience than any kind of real need for it.

Some kinds of indoor stuff can be easier to map if calling it out on paper. I always remember the groans and slow down in play when you got to caves. But a VTT overcomes all of that.

The main reason I still use a grid is for mapping with a snap to grid option. Putting in pillars, tiles, walls and so on is much easier. Getting perfect 45 degree angles and so on is hard without some kind of snap action.

With a VTT you can place down an area template for fireballs and measure distances with similar types of ruler. Personally I don't think its a good idea to let the players get a good idea of exactly how far their bow shot is until they have let fly. And I don't particularly like the restriction of tile based movement or facing. These all seemed like constructions to make the game play easier from being able to say to DM ill move 5 squares north and for the DM to say that you can have exactly 3 squares worth of attackers around you. In some ways the grid gets in the way when the perfectly round fireball template lies half way across a grid.

So I wouldn't want to be without the option but generally, no, I don't need no stinkin' grid.