@Deozaan: Well, having made the initial investment of your time, you should perhaps have persevered and experimented a little longer before throwing in the towel, and then you might have realised some good returns - as I did, in fact.
I had similar thoughts to you, but persevered and banged in all the extensions that I felt I needed (minus the AdBlock one), taking a suck-it-and-see approach and half-expecting to break the camel's back, but no, the adverts simply never occur and the thing's performance seems just fine - very good in fact. I have some minor criticisms of the software, but I am pretty sure that those will be sorted in due course. Even my 6 y/o son prefers Slimjet now - the acid test.
Conversely, as a FF die-hard and after a great deal of perseverance on my part, and in the continuing hope that things would improve, I had to face up to the reality that Mozilla had pretty much conclusively demonstrated to any sighted observer that they were not going to cease screwing up or killing their formerly excellent Firefox product, and so I reluctantly voted with my feet.
As in a lot of major changes that one sometimes makes in one's life, one wonders afterwards "Now why didn't I do that earlier?"