Well, I'm torn about the Trex. It's not all that their marketing would have you believe it is. But in a nut shell, here's my assessment:

Pros:
Apparently not as prone to mold staining as other brands which have class action law suits if you Google around a bit. I was going to go with a lower end product but was scared away by the mold stain stories. This was more or less my only reason for pony-ing up for Trex.

Cons:
Astronomically expensive compared to a decent cedar. Twice the price.
It scratches easily. You have to be mindful of moving your power tools around on it or you'll scratch it.
Don't believe the marketing - it does fade some.
For $3.00 per lineal foot I'd expect some grain variation to give at least SOME impression of an organic material like wood.
It looks exactly like what it is: A plastic deck.

The concealed fasteners are not worth what they charge for them. For that 500 s.f. deck that I built they wanted (no joke) $749.00 for concealed fasteners. I can look at Grip Fast screw heads all day long for that kind of money..

But to answer your question the heat hasn't been an issue.