No real complaints here. I haven't had tuning troubles. At least no more than other engines I've run. May be low on power. But it's still fun. Isn't that the point? BTW, I just ported mine. Don't see a huge difference yet. Still fun.
I think the TRX is a great motor learn the T-Maxx with. I found it easy to tune, holds a tune great, and it's got enough spunk to keep you interested. PLUS, you can port it and get much more power from it.
If you want to cool it down put a Hardcore Mutant Head on it. They make 'em for the TRX and the OS. Run it as hard as you want, bring it in, and put your hand on the head for about as long as you want. It is well worth the money.
I have the TRX in my Nitro Sport and that thing really hauls!! The trick with the NS was to remove the baffle from the carb. It's like night and day. I still keep the baffle so I can let a less experienced R/C'er try it out. But really, I like the TRX. I haven't had any problems tuning it. I'm going to switch back to the TRX in my Maxx becasue my little OS .12 just ain't puttin out the ponies.