Just a few points to add to Robin's post:
1) While elves get a bonus with longbows, elvish assassins can't use them (unless you use Shadowkeeper).
2) Half-orcs may have a bad complexion, but their victims will never see 'em
Wouldn't you rather give that girdle of giant strength to someone else so that two in your party can have giant strength?
3) Yes, their thieving skills generally suck, but if you're familiar with some of the magic items in the game and assign your points accordingly, you can alleviate the problem somewhat.
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Make sure your assassin's Move Silently and Set Traps skills don't naturally exceed 80% and the Hide in Shadows skill doesn't go over 55 or 60. The BonusCD merchant in the Adventure Mart can sell you the Mercykiller Ring, which increases all 3 skills by 20%, and you can get some +5 Leather Armor called the Night's Gift for completing the Umar Hills/Shade Lord quest that increases your Hide in Shadows by 20%. Then you can start devoting your points to the other skills - just make sure you have another thief in the party until you get them up to an adequate level.
BTW Robin, I thought your post was very informative and well thought out
[This message has been edited by Desuma_Malevois (edited 06-18-2001).]