I have concerns about the 810 chip, it has been underwhelming so far but it is a great price and they actually have the bands needed for T-Mobile this time.
At the same time, I'm interested in seeing how it compares to the new Nexus 5; I'm interested in trying out Project Fi. While Fi currently requires the Nexus 6, the rumor is that the new Nexus 5 will be the second phone allowed.