Got the XT yesterday and have been playing around with it. A few quirks that are a bit annoying:
1) the temperature on mine was way off and they had to reset something on their end to get it to normal (seems like it's been OK so far but it was reading 40F and if I tried to calibrate it, it either didn't do anything or made it worse...)
2) the IR LED seems kind of bright and obvious - maybe that's just how it has to be if it's the only form of IR illumination though? It's more noticeable than a single IR LED on my Amcrest though (but probably because there is a ring of those IR LEDs - couldn't they have just added several more IR LEDs instead of a single on on the XT if that's the case then?)
3) at least for me, the IR LED doesn't turn/switch back off after normal lighting resumes. So if you have the lights on in an otherwise dark room, then flip them off, the XT's IR LEDs will kick-in but if you flip the lights back on the IR LEDs will not turn back off.
Other than that, it seems like it would hold up well outside. Ironically, I'm scared to put it outside in case someone is bold enough to rip it off though lol. It feels a bit heftier than the original Blinks, as someone above pointed out.
In terms of syncing with the existing Blink module and ST - no real issues so far. It was pretty easy and the device showed up on my list of ST things after adding the device in Blink.