I'm going to take a look at the S9 deal that Best Buy is offering later this afternoon. This would potentially save me a few hundred dollars if I went though one of the other big-name phones at the moment.
I've had the 10 for two years now and even though it's still running well for the most part, I can't look past some of the issues HTC has going on right now. Otherwise, they'd be on the top of my upgrade list. Sprint also isn't even offering the phone this time around, so hanging onto HTC would mean the added hassle of switching carriers right now and paying more under a different plan. Combine that with other things (jack v. USB-C audio, warranty issues when the phone is bought from HTC directly), and it seems like going through someone else might be for the best.
I thought about getting a U11 online too to tide me over until next year. But the phone isn't really available anymore and even if I bought it used, I'm concerned what might happen if something eventually goes wrong there without any insurance of sorts.
The good news is that if I did upgrade now, I could hold onto the 10 as a backup phone in case the next one breaks somehow (and still give it some use as a "workout/walk" phone, which the M8 sort of serves as right now). It's a shame because I would consider the U12 if a few of these things were in order, but it doesn't look like that'll be the case for this cycle (assuming they have more in the future).