I'm still using my EVO 4G on Sprint as well, running Cyanogenmod 7 on it since the ROM came out and it's been working great - and still does - I just need a change. I never really bothered with the WiMax 4G, even when I lived in Richmond, VA that's covered in it I was never able to keep 4G signal inside buildings. I'm a little worried about that with Sprint's upcoming LTE 4G too due to the wavelength they're using for it, but we'll see.
UPS is now saying my 16GB Blue S3 should be delivered tomorrow!!