In my opinion bards absolutely worth having. Mainly for three reasons:
1)They have really high lore. No more identify scrolls/spells or paying for it. Just give the item to the bard, examine it and phuf.
2)They are pretty good backup-mages. Although not as powerful as pure ones, but still pretty decent. Don't forget Tenser's Transformation (or whatever it is [img]smile.gif[/img] ).
3)And their song is very good for buffing. Especially if you have TOB, then you have to have bard and choose Enhanced Bard Song. -10 to bard's armour class and 10% to MR and for party members it gives +4 to hit and damage, -4 to AC, immunity to fear, stun and confusion and normal weapons(!) and 5% to MR. I just recently hit 3000k in exp., I chose this ability and then I just sit back and watched my fighters kicking some serious ass.