Picked up Fable 3 this weekend, quite enjoying it actually. Worth a tenner anyway.
Played it for like 15 mins and got some really bad lag, not really sure how to attack... when i click the attack animation doesn't do anything.. :/
yeah the combat system is a little different... you'll get used to it. watch youtube videos.
assuming you dont mean video lag then it's because you need to time your mouse clicks for fluid fighting - until you get the hang of it you'll be stopping and breaking your attack because your clicking too much.
don't judge the game on the first 2 chapters either but I have to say that the first level: kaer morhen is pretty poor - the game gets much better v.soon.
You have to time your attacks, if you are playing on normal then you have to click when the cursor changes.
Also, read manual.
And if you get low framerate...change settings or upgrade PC.