don't know what to think anymore…
Reset my network settings today, lost signal during the workout, got back upstairs.
Check some web-links, 3G network was working fine. Had my girlfriend call me before making any calls with the phone, she got through alright.
I really don't know what to think. If I conclude that it is now working flawlessly, my guess is I will find out that it's not working. If I remain skeptical, checking my phone every 15 minutes, keep turning airplane mode on and off, I guess it might just continue to work or I might not ever find out that it is not working.
It seems to have solved the issue, from time to time. Some say their problems are gone, some say that they never had these issues and they started after the update. So iOS 6.1 with LTE support fixed issues for some, ruined it for others and for some, just poses as a "false positive" since it seems to work, but really doesn't. So, now I can't trust the phone when it seems to be OK.
Talk about jumping the gun on pushing a new product, obviously Apple was no where in the vicinity of close to being able to release iPhone 5 and ensuring functionality, just as bad as providers pushing a product not supported by the service their selling, flaky SIM-cards… I guess extremely disappointed describes the situation well.