I disagree on several points.
1 - Why a 1/2 elf? Go with a pure elf and get better sight, saves against certain spells, and +1 THAC0 in longbow and longsword. IMHO the only reason to be a 1/2 elf is as a bard because they are at least better than a human (your only other option)
2 - There was a time in BG1 when I swore by elven fighter mages, but I came to realize something. My spells weren't as effective (caused less damage or last for a shorter time). There are 6 characters you can play with, there really isnt a need to double up on the four basic food groups (fighter, mage, cleric, theif) just for one character.
3 - Playing as one is agonizing since it takes so much more time to level up. There is nothing worse than getting this cool new magical weapon, but having 250k more xps to get before your next prof. Or waiting for the next level spells.
4 - In BG2 you wont be able to cast from memory those high level spells. Sure, in the expansion things will be better since even a multi mage will be able to cast 9th level spells, but they will always be cast less oftun.
5 - Then there are those stats... Instead of 3 vital stats for the fighter (str, dex, and con) or 2 vital stats for the mage (dex and int) you now have 4. Since I don't want to be totaly clueless (low wis) or but ugly (low char) There aren't enough points to go around.
I'm not trying to flame you. If you love the F/M then by all means enjoy your game, its just not my cup of tea.
cheers