We brought it up in our Android 6.0 primer video: expect bugs. Especially expect them in more front and center areas at first blush before the updates eventually come to patch them. It’s not a rule exclusive to Android, just ask iOS. Twice.
But T-Mobile troubles have appeared (no, not those T-Mobile troubles) and it involves LTE reception on Nexus 5 handsets. One Reddit user noted 3G reception in areas normally flush with LTE. Another user, from AT&T subcarrier Cricket also had a similar experience which got troubleshot with a toggle on-and-off of airplane mode.
Another T-Mobile customer ran speed tests at no bars of LTE on a Nexus 5 and get better-than-average results at a signal strength of -90 dBm.
We’re not sure if the problem affects radios or if it’s screwing up the system signal reading, but a T-Mobile employee and Redditor is filing an internal report.