I've been thru the game quite a few times solo, it's really not that hard, however I would not suggest taking a druid thru as a first attempt. If you do a search on the word "solo" in the forums you will find HEAPS of posts with tips and tricks about playing the game with only one character. Also check out the main Gamebanshee BG2 page, in the startergy guides there's a section devoted to soloing either SOA or SOA & TOB.
The first time I went thru the game solo was with a Fighter/Mage/Thief. This character is an excellent intoduction into the solo world
If your seriously thinking of going solo, do some research in the forums and the Gamebanshee site, there's loads of tips to get you started, and help with any of the major parts in the game.
@ Arcane
Keep it coming