HTC has really turned things around this year with the HTC 10. It might not be the best at everything, but the fact that it's even competitive is a big deal for the company. T-Mobile customers who want to pick this device up on a payment plan can do so today, plus you get some freebies.
The T-Mobile version of the device will be locked to the carrier, but it's a few bucks cheaper than the $700 unlocked model. It's also available on T-Mobile's payment plans for $28.34 per month ($679.99 full price). Keep in mind, you'll probably get slower updates than you would with the unlocked version.
If you buy from T-Mobile right now, you can get a free HTC Ice View case and a space fast charger. Together that's an $85 value. You can grab the 10 from T-Mobile's site or in stores, but it looks like only the silver version is available.