In reply to topee:
I've not been in winter but spent a few weeks in and around Mestia a few years ago.
There is considerable snowfall which cuts off some of the villages (Ushgulli is often snow bound for 4-6 months). There are some small ski areas with chair lifts but I suspect there's not much scope for nearby ice as they are mainly located on the more gentle grassy mountain sides.
Nearby Mazeri is much quieter than Mestia but has one of the best valleys for waterfalls. It's a couple of hours walk from the village to the main waterfalls but there are farmers tracks which many locals will happily drive up. We visited several glaciers and other mountain paths, the guest house owner's cousin (or something) was happy to be a taxi driver for about £20 all day, it really cut out some of the valleys approaches.
Bus timetables from the towns to the cities are more guidance than a fixed schedule. £1-2/hour of travelling is fairly normal. Although there are large coaches access to the smaller towns is normally on minibuses. If the bus is full, they often stick a plastic stool in the foot well as an extra seat. Everything is very cheap, including the amazing Georgian wine. It was largely a cash based economy outside of the big cities. It's hard to get Georgian Lari outside of the country so use the ATM at the airport, euros are accepted in some places but at very poor rates. Booking.com was useful and normally had "cash on arrival" as the payment method.
It's a fascinating country and well worth visiting.