Just got my OnePlus One on Saturday which replaced a S4. I'm using GSM. I am getting far worse LTE reception than I did with the S4 in the same locations. For example at home I used to get full bars, now I get one. Same issue at work. I actually get better signal quality with T-mobile than sprint, although the data is slower. There is a way to switch the networks on the phone.
1) enter the service menu by dialling ##4636##
2) enter "Phone Information" menu
3) change "Set preferred network type" from "TD-SCDMA, GSM/WCDMA"
4) to "GSM" (see EDIT1&2 below!)
Switching to GSM only I get nearly full bars. I haven't gone as far as rooting the device or flashing a radio, looking to see if any smart Ting users with the OnePlus One have found any work arounds. I've seen a lot of posts on the OnePlus one forums and reddit, but wanted to ask here since I am using Ting. Maybe it doesn't matter since it's all actually T-Mobile towers. I have taken a couple calls though which didn't drop and sounded clear. Fortunately not a huge issue since I rely on wifi for data. But I do occasionally use data like with maps.