Originally my 2mm figures were based as Div/Bde units on ~2-4cm squares, on 4cm hexes. Far too fiddly, and Hexon is now my preferred grid of choice. So I decided to rebased on 8cm hexes, which sit nicely in the Hexon 10cm hexes and allow for a nice layout of troops that actually give the sense of a Div or Bde drawn up in a couple of lines. There's also plenty of space for a unit label. At this scale it means that each ground hex is about 500m (for Div) or 250/300m (for Bde), so certainly at Div I can accommodate big battlefields (my table gives me about 10 x 20 hexes, so 5km x 10km).
As ever though there's then the issue of scenery. I originally bought some 2mm scenery to go with the figures (all Irregular Miniatures I think), but whilst the little village models are nice, they actually look far too small on my relatively large table, and the mini trees/forests just look silly. So as the top picture shows I've used my 6mm trees, and they look spot on. For the buildings I've got some 1/1000th models (Brigade Miniatures) which I originally bought for my 6mm modern gaming, but they ended up looking too small again (!) for that, but seem just about right as in the above image for 2mm! So come the New Year I'll put in an order for some Horse & Musket suitable 1/1000th buildings from Brigade, and make up some nice 10cm hex dioramas. One ide I'm playing with is to have the outer edge of the hex separate from the inner, so that when a unit is in a town you remove the central portion and replace it with the unit!
Rules wise I'm going through this gradual bucket-of-dice conversion. So whereas that first Borodino 2mm game gave birth to Steady Lads Steady (my main in-house rules), I'm now doing a bucket-of-dice version of SLS drawing on some of the things I've done with the Medieval rules I'm growing out of Hordes and Heroes, and with a bit of Blucher influence. We'll see how they run.