The HTC Mazaa is one of those strange devices that are hard to really get a hold on. The device is essentially a beefed up version of the HTC Trophy, and has been given away as a gift in a couple of Microsoft developer contests, but it's a device that may never actually make it to retail. That said, it should serve as a good benchmark in what to expect with the new generation of Windows Phone Mango devices.
fish tank test from Microsoft, the Mazaa ran at 47 FPS to the HD7's 30 FPS.
The Mazaa does include a CDMA/GSM dual band radio, so it could theoretically come to Verizon or Sprint, but there has been no confirmed release announced for the device. Still, it looks like the performance capabilities of Mango phones should be pretty solid.