M7 vs M8 on Sprint

[i VTAK]

I just got an M7 for a family member and I'm wanting to upgrade to the M8 for myself. A tech at the Sprint store told me they had a lot of complaints on the M8 and said I shouldn't get one. Add that to all the online complaints I've seen about the M8 and S5 on Sprint having network issues because they use a new technology and I'm scared to get it. My LTEVO is on its way out and I need a new phone. I may just get the M7 since I've had time to play with it and it performs well. The only reason to get rid of the LTEVO is because the G Sensor broke and its annoying using and app to rotate for different apps.

So basically I'm asking if anyone on Sprint has upgraded from the M7 to the M8 and what are your impressions on call quality and data performance.