yeah, I had a particularly fun game once with the Bradeline's Well. I waited till pretty late game to start playing with it, got 4 Wizards with Divination 3 and Sphener with high Command over near it. 7 times in a row it spawned groups of nice baddies, all of which I stole. I got some neat hero units out of it, some animals, and I think a few werewolves. It's a very nice unit-milking tile if you have units with a high level of Command or Divination 3 Wizards. You can milk it for XP, but I think thats a waste.
As for early game, I probably wouldn't toy with the Well unless I had about 12 warriors sitting around on a stack to "hopefully" deal with the nasties that pop out. But of course they could just ignore your stack and just go straight to destroying your cities. Bear in mind, there are some nasty groups that can spawn out of this, think 8 Strength Ogres and 7 Strength Assassins in groups of 2-4. This is NOT a early game tile to explore, unless you want to cheat and keep reloading till you get a fun result, but that will only result in pissing off Acheron and making him spawn in your capital for being such a lying cheating tool..... or so I've heard.