I've been running one for about 1500 miles with about 85% of those are highway cruising. It does make a noticeable increase in power but I haven't dynoed or timed it so how much I can't say. Playing with it Durning normal cruise I can't really tell a difference when changing to different settings. The mpg economy screen in the dash is reporting about 2 mpgs better than before I had it installed, so it is doing something, but I haven't hand calculated the mileage to verify that either(not really concerned with mileage). As a side note, I've been using sport mode more often since install, but even leaving the transmission in normal mode you can feel it has more power down low. I have yet to try manually shifting and just let the transmission do its thing in either mode.
I did log some via HPtuners and I can't really see a noticeable increase in egt but I'm no pro especially when it comes to diesel.
Over all it will hold me over until real tuning is available and im satisfied with it. Might jump over to the Banks Derringer once it's available if HPtuners still hasnt cracked the ecm by then, and sell this since the Derringer is supposed to keep the extra power longer. Check out the comparison video Banks does on the Derringer vs the other guys on the L5P if you haven't watched it already. I suspect that similar things are happening with the LM2.