I am new to longarm quilting - my husband bought me a Gammill last summer. I have about 25 hours on it so far and have only had one major problem with tension - I would have caught it earlier if my friend hadn't been distracting me - it was her quilt and she helped do all the "ripping". Once she was gone, I reloaded it onto the machine, went to the local quilt shop and talked with the owner, then came home and adjusted the tension on the bobbin case and quilted her quilt in no time at all without any issues.
I bought mine used and haven't had any interaction with the representatives in our area. I do know that I visited the quilt shop they are located in and left feeling "ignored". I will have to give them another chance, but it will take me awhile. They aren't close by and I don't get there often.
My biggest problem with owning my longarm is CONFIDENCE! I am gaining more each day with each new project.