I haven't closely examined the blast effects to the point of counting how many squares are affected, but my take on converting those to a hex grid was to make them what they should have been in the first place – cones.
Cones work great on a hex grid. They are horrible on a square grid. So in 4E with it's bias towards all things square (it's hip to be square!), they have made spheres and cones into cubes with the awesome power of their non-Euclidian Mathmagicians. Even the *bushes* on the battle grids for KotS are kind of squared off. Perhaps the gnomes are sneaking around clipping the hedges throughout the woodlands into nice even squares, which would explain why you find them in gardens all the time pretending to be statuary.
In any case, I will count out the number of squares affected by various blast radii, and come up with some cone templates of about the right size. Perhaps for some attack types such as lightning the blast should be a line effect. That should be fairly easy to adjudicate if you decide to go that route. Don't restrict yourself to cubes!
I know that the number of hexes affected by a burst 1 radius is smaller than the number of squares would be, but as you already pointed out, the number of people who can surround you is also less on a hex grid than a square one. I think the trade off is even there. Furthermore, I can't imagine 8 people being able to surround one humanoid without sharing "squares". They wouldn't all be able to swing a sword freely. Even six guys is kind of pushing that, but is more realistic.
We're going to keep using our Chessex hex grid, and convert spell effects over to hexes. I'll work on some templates for cones in my copious free time. Heh. Personally I hate the firecubes and sqared off caverns, bushes, and architecture that 4E seems to have embraced. I have no trouble drawing square buildings on a hex map, as I make use of an arcane device called a ruler to assist me. So WotC can be square if they want to, but I'm all over the hexes.
