I'm in the US on T-Mobile and 4G/LTE works great. I'm in Chicago, so my area is typically heavily congested, but everything works well.

For the record, I flashed on top of the latest Emma image (coming from the community build, I just wanted to make sure). I flashed a EU version on accident (I was still on my Finland VPN, so Emma populated based on that) but everything still works as it should. I don't think there are any region issues.