Raymond has converted MTH engines to battery for me. I have one boxcar for the battery, and another with the TIU in it. The system works without any problems, at least for me. The only problems I have are user error. I run my trains on a community layout and this is the only way I could get my MTH system to work. For my use this system is great.
I can say that if I had my own layout, I would probably use track power. I would rather leave the equipment stock from the factory, although, I do trust Raymond's expert work.