im just not sure, i kinda like the idea of having a specialist and have never dual classed in any game (bg,iwd or bg2 ) im planning on playing the game through a second time (when i finished it for the first time)and thought about a fighter /thief whats the best level to dual class at ,is this a good combi,what restrictions are placed upon you and is it in the end worth it

Well, in BG1, I found that a Fighter/Thief was my favorite. Lvl 7 fighter / Lvl 8 Thief. I went up to a level 7 fighter for the extra 1/2 attack per round. In IWD, I think I went to a level 13 fighter then dual classed to a thief. I plan to do the same in BG2. It is just awsome being able to hide in shadows then backstab for 5x damage and be a grand master in long swords.