I bought their SR59 (the mtce free version) last year.
See: http://www.batterycentralmall.com/Batteries/TurboStart/Script/SR59.html

I was replacing an R59 I got from another source about four years earlier. This time I wanted to see how the better one held up. Plus, buying acid to fill the first one and then dispose of a lot of unused acid was a pain (a couple boxes of baking soda took care of it)

So far the maintenance free has been OK but it is not normal car battery use so it's hard to tell how robust it will be over time. I have a battery disconnect for safety and clock and radio drain and throw a tender on it periodically to top off the charge.