Is AT& T High Speed Internet broadband?

I am sick to death of Comcast's overpricing for cable & internet service, I am going to go with another cable TV provider but I have to say Comcast Internet cannot be beat for fast, and for no glitches.. but the price is getting outrageous. I am thinking about the AT & T "High Speed " Internet offered now, but what will I sacrifice. (I have the fastest Broadband that Comcast offers and it really really is blazing fast for my 7 year old computer (512 mb completely updated as much as possible without putting alot of monery into more memory cause I have the old Dell kind thats too ridiculously expensive (old alloy or something) , it would be more prudent to just wait til i can buy a new puter, but my puter works excellently anyway, so is AT & T gonna disappoint me if were to switch from Comcast ?