A few comments on the Green Diesel Engineering software mentioned earlier. From their web site, it looks like they don't support newer than chassis year 2008. For those models than can use it, it gives a nice bump in performance and a small MPG increase. The newer sprinter engines that use the def fluid have increased power from the factory, possibly just as much as GDE provides with the non-def models. What's more important IMO is that the GDE software enhances reliability by disabling use of the EGR system and swirl valves. Failure of either triggers limp mode, which is not only annoying but potentially unsafe because you're lucky to go over 20 mph with it. The price of repairing the swirl valves is a few thousand $. As already stated, the sprinter is great unless it's broken. When that happens it can be an expensive nightmare. I've been lucky so far.
