Never was much of a Holley fan(sq bore) and the Rochester types (spread bore) are great when they are set up right. My favorite is the Carter AFB and its decendant the Edlebrock series. They don't leak. Metering rods and jets are changed from the top and they are easy to set up for different conditions. Unless you know what you are doing, stay away from the Carter Competition series. They have no vacuum ports or choke setup. The new Edlebrock has both ported an non-ported
Gas milage. You've got to be kidding, right. Maybe 15mpg
I've had two Q-Jets and I now have an Edelbrock 650 cfm Thunder Series AVS carb. The two Q-Jets were nightmares. They leaked, they stumbled, and they generally ran like crap. And the second Q-Jet was brand new from GM. I got the Edelbrock last year and took it out of the box, bolted it on and haven't touched it since. It starts and drives like fuel injection, requiring almost no warm up time. Idle is noticeably smoother and I can idle 100 rpm lower than the Q-Jets. No leaks to worry about either. I won't have anything but an Edelbrock on my car from now on.
I have had a Q-jet, Holley and now have a Demon. My only complaint with the Q-jet was the inability to get rods and jets locally. Square bore carbs have thier own set of problems but at least I can get parts for them anywhere.