Hahaha! After thinking that I was the only one that had an HTC 8XT you show up, lol! I had an HTC 8XT on Sprint up until January of this year and now have a Lumia 1020 on Cricket. Actually I still have the HTC 8XT plus a Microsoft Band if there are any tests you want me to do let me know.
That being said I did use my Band with the 8XT and it faired pretty well. Granted there have been updates to the Band and the Microsoft Health app since I last used it. Everything worked great, I could use Cortana, texting from the Band, email, etc. The only issue I had was that I noticed after each notification my Band received it would temporarily disconnect for about 5 seconds and then would be connected again. If I got any additional notification during that 5 second period the notification would not show up on the Band.
Also of note I was using the latest firmware provided by HTC (December release if I remember correctly) and was running Preview for Developers with the latest Windows Phone 8.1 release. Like I said I still have the phone plus the Band so let me know if you have any specific questions or tests you would like me to do.
If you do decide to get the Band, (which I would say go for it! It really does get along quite nicely with the 8XT) I can help out with any issues you might come across.