UBWS does work with archery.
my archer uses a ubws kryss and it works very good when i run out of or dont want to waste bolts.
also the fastest bow in the game is the magic shortbow. get one with 35+ SSI
the fastest crossbow is the repeater but.. you do more dmg with the reg crossbow with high ssi (30+) on it even tho its slower.
think what faith ment to say is you cant use a ubws bow without archery skill, those dont work.
also you dont gain archery skill with a ubws wep

archery is a very slow skill to raise, specially since you miss alot and you cant go after the bigger mosnters easy.
what i did on both my archers is go after ettins and stuff in despise, then find a party that is doing peerless. like lady mel.. or goto doom.
i gmed my first archer from 50 skill in doom in one week..
do the new haven quest if your not to 50 yet.
at first just stand back and hit the knights and stuff, then rotting corpses. they take so long to kill you almost always gain a full point in skill before its dead.
just buy about 5 quivers and insure them all, then fill them with arrows..
remember to loot all the corpses you can, people usually dont grab the arrows.