I do pick up a LTE signal inside my office building on the West Side of Manhattan, and it works relatively well with good signal.
When I am at school though (Downtown Brooklyn), which has cement brick walls, data service can drop all the way down to O speeds, and signal strength is very low.
Periodically it would switch from LTE to 4G but its not that big of an issue. Cell service in the Subway is great as well, something Verizon I believe does not have yet. Many major stations have LTE and 4G service down there, and I have been able to grab my entire news feeds from websites within the small periods that I am on a train thats stopped at the station.
If you are talking about reliability, make sure the signal strength is (a little) over 2 bars, if it drops, your call wont make it.