Ain't nothing wrong with the GO motors. If you break them in carefully, tune them right, and look after them (like any motor), you will get 10 gal or so.
I think most people have trouble because they are too impatient with the break in. These motors are very tight when new, and just need to be broken in properly. No motor will last if you just run a tank through it and then cane it. I am sure there is the odd šlemonš out there, but you get that with any brand - even the top dollar ones. On the whole I think you would find them one of the most reliable motors at the track.
5 Ports are very economical for their power output. 10 - 11 min with a 6.5 mm restrictor is quite obtainable, especially with the modded motors.