The up-side IMO is the combat. I have never played an rpg where the combat system is that good. The Chasm of the Dead is doable with a party of level about 11 if you know what you're doing, but it's still quite enjoyable with a level 30 party. I've never played a game with such a forgiving combat a.i. without the "cheat" of increasing the monsters' strengths as the party level goes up.

The down-side is the bugs. People (Bones in particular) have put some sterling work in to get rid of some of the bugs, but others remain. One thing I will say - ALWAYS take a back-up save before entering into a promotion dialogue. You only get one chance at this, and if you blow it, the only way you'll promote your character is by using a hex editor on your savegame. It's a good idea to keep regular backups anyway.

Two final things. First: IMO, Ranger and Paladin are very poor characters. If you want a "half and half" character (i.e. a fighter/spellcaster) use a druid, and get him/her to GM level in Unarmed and Dodge. You'll get a very bonny melée fighter with good magic skills. Second: there are two promotion quests that you cannot complete without actually promoting a character to that rank - priest and lich. Personally, I wouldn't run a party without both of them anyway, but again that's just my personal preference.

My two favourite parties are the general purpose assassin/gladiator/priest/lich, and the all-magic one of priest/druid/lich/mage. The latter one is fun, especially on the bottom floor of the lich lab.