The Russian normal route is 5A, the Georgian one 5B. The Georgian route (south pillar) is 2200m vertical with 45-55° snow max, 2-4 UIAA rock. Brief route description:
http://www.skitalets.ru/books/svanetia_naumov/ route Nr. 111. Also:
http://www.stadler-markus.de/kaukasus/f ... netien.htm I recommend against taking their descent route. You will not find it on your own and it is in really bad shape, with several re-ascents up 60°+ slopes (I was on that route, too). When something goes wrong, you are in the wrong country with all the trouble associated with it. Rather descent the ascent route (south pillar).
The south pillar route never gets really difficult, but the difficulties are constant. The route takes about 6-7 days, or more with bad weather. Going with somebody who knows the route is strongly recommended, because of route finding (particularly when descenting). If go alone, do not go the first time you are in the Caucasus. Get experience elsewhere, get a feel for it. Go to Shkhara when you are sure you can do it. Not a good route to "try".
3B/4A and 5B are very different leagues. There are very few 4A and 4B routes to the 4800m+ summits in Georgia for preparation, really only Tetnuld NE ridge (nightmare to get to) and Ushba north 4A (probably best choice). Russian side has a few more (Dych-Tau, Koshtan), which are also a bit more similar in character to Shkhara. All south face routes of Janga-Tau 5058m are 5B too and there is even less info. Other 4A routes are mainly due to difficult approaches and glaciers (Shota Rustaveli and traverse to Janga-Tau - just came back from there, Gestola, Katyn). I suppose some routes in the Alps may serve for preparation too (Brenva and Walker Spur or Bumiller Pillar come to mind, but I do not know the Western Alps at all, really), but they will not gain you any experience with Caucasus weather and logistics.
Martin - I do not really live anywhere constanly currently, I lived/worked the last years in Canada, Norway and Japan, but home is Austria, second home is Georgia (-:
Take care,
Peter