If you get one that works, it will be no different.
Mine runs great.
Flash or reflash makes ZERO difference, the only variable was how well it was flashed. The early ones were done by untrained people. Some worked, some didn't. It's the same as flashing a rom.
Designed for Sprint? Come on.
What do you think Virgin is. There is nothing different or magical about Virgin compared to Sprint. In fact, you can flash almost any CDMA phone over and it will work perfectly fine, other than MMS. I did it with an Evo 4g, it ran perfect. I know people with Evo Shifts, Marquee's, and more all on Virgin that run perfect.
Go ahead and keep thinking there will be some magical difference, but you are only fooling yourself. Will there be less issues? Sure because it will be flashed by HTC in a controled environment where they are more likely to have better quality control, but if it works, it works. Doesn't matter who flashes it.