Upon reflection, I went and bought Avadon 3. I generally like Spiderweb and want Vogel to do well, and Avadon 1 was decent enough that I actually finished it. I remember enjoying Avadon 2, as well, until the corruption trashmobs and HP bloat ruined the game.
So far, so good. I played up until the point where you meet Redbeard. I never finished Avadon 2, but if you've played Avadon 1 to completion then you'll know enough about the lore to get by without trouble. This game definitely doesn't lay out the foundation for the story as well as any of the Geneforges, so you do need to read up a little if you're not familiar with Avadon.
Still has the dumb, 3-man party mechanics with lame and rigid character types. Yet, little differences make it more fun than the first two. If you play on Hard difficulty, the friendly fire makes things a lot more interesting. Health and vitality both regenerate quickly out of combat. I'm kind of pissed that the summoning item I bought (ogre statue) disappeared after one use, but whatever. There's a good number of consumables, but honestly the combat has been pretty easy so far; I'm playing on hard difficulty with a Blademaster, Shadowwalker, and Sorceress.
There seems to be a number of meaningful, faction-related decisions. Reminds me of Geneforge, but let's see how it plays out. The general story itself was slow to get going, but now that I've met Redbeard I'm very interested.
One little annoying detail is that I have to change my desktop resolution settings in order to affect the game's resolution. If Avadon is refusing to cooperate, just lower the desktop resolution and voila, no need to squint anymore. This is not unique to Avadon, I've had the same issue with other Spiderweb titles.
If you completed Avadon 1, or at least enjoyed it to some extent, then I'd say go ahead and buy this game. It improves upon the original, and right now I'm into the story.