The back cover is a bit soft, yes. People have been bending the camera aluminum ring because they were too rough with taking it off for the first time.
When it comes to the EVO vs the Triumph, the EVO wins in every possible way. I'm more surprised you have a working Triumph over having a defective EVO, actually.
The reason I had to assume it was buyers' remorse was because people get excited, have expectations and then get sticker shock when it's not quite what they thought they wanted. Especially now as off contract phones are getting better (and more expensive)... I predict a LOT of disappointed people once they finally plop down $650 for an iPhone on Virgin or Cricket.
Now, I'll admit I was a bit harsh with one of the statements and it appears worse than it should because I didn't expand upon it... but 4G isn't a gimmick. It works great in my area, but it's also not a nationally provided type of coverage. If you have a weak 4G signal, it'll drain faster because it has to amplify the signal more.
If you're seeing horizontal lines when in 3D mode, you probably have the phone too close or too far away from your face. Yes, it's a gimmick, but it also works fairly well. It's not much different than the Nintendo 3DS. Just gotta hold it right and let your eyes cross a little.
In the end, I didn't buy the phone for 3D and the addition of 4G is just a bonus. It's still a very decent phone for $300 and $35/mo. Consider getting yours replaced and giving it one more shot.