I'll go ahead and say it: gnolls are bad. I don't mean morally bad (though they're that too), I mean they're a horrible, underpowered choice. You may think samurai and monks are bad, but trust me; gnolls are way worse. If optimization potential was water, gnolls would be somewhere on the lunar surface.
With that out of my system, let me explain just why they're so bad. The answer is simple: humanoid RHD, which are somewhere south of aristocrat levels in terms of utility. Gnolls start with two, which combined with their lack of useful abilities sentences them to -0 LA already. If I wanted +4 strength, there's other ways to do that, most of them quicker.
To be honest, I think gnolls are bad enough in their current form that one could just remove their RHD and let people play one as a normal race. Seems to me like that'd put them somewhere between regular and water orcs; a good melee race, but by no means the best, and with other races often fitting a particular build better.