Okay, here we go, if i can remember them all. TRX .15, TRX 3.3, Novarossi .12, OS .12 and .15 CV-R, HPI .15 (came with rtr RS4), HPI .25, LRP .28 spec 3, Mach .26.

TRX .15- i was ok with these engines. Always seemed to run ok, although they usually run hotter than most other engines i've used.
TRX 3.3- makes gobs of power if tuned right, but i absoluly HATE these engines. I have had nothin but problems out of them. And that soft composite carb never failed to strip. And whats with those plugs on the carb? A 3.3 with an OS carb, Boca bearings and Davis rod was bouncin around in my head for a while. But too much $$. Would b killer tho.
Novarossi .12- loved this engine. probably one of the best engines ive had the pleasure of running.
OS CV-Rs- What can you say? Great engines. Used quite a few and never had a prob. Holds a tune awesome.
HPI .15- ehh it was ok. not my favorite by any means but it worked.
HPI .25- got a used Savage x and this engine was in it. Ran ok, but not enough power.
LRP 28r- Love it! Currently whats in my Savage. Mine loads up a little too on the low end, but only for the 1st half of the tank. Darn mid tank lean. After half the tank gone tho, it'll happily flip my extended Savage on its lid.
Mach .26- My buddy just got a used Savage with this engine on it. So far so good, but we've only ran it for a minute or two.

Only engine i ever really hated was the trx 3.3. Actually, i have a junk one my neighbor and i are gonna try his barret .50 on. Justice will be mine...