Dinan matches BMW's 4yr/50k warranty so you're good there. As with any ECU mod it increases the work on your engine somewhat so if you really are hard on the car it may shorten its lifespan/increase wear and tear proportionately but that is true with any engine mod. However I haven't heard stories of Dinan ECU modded cars falling out all over the place so I'd say he's pretty good for the added cost. Some go other routes that are cheaper but Dinan is still around and I think its the warranty helps from a piece of mind standpoint.
I did Dinan Stage 1 when I got my Eissenman Race done last Nov and its great! Thought about going state 2 or 3 a the time but Stage 1 was just the best bang for the buck. I think Stage 2 is still going thru CAFE testing and awaiting certification so my local dealer wanted me to wait until doing it but I'll likely go to Stage 3 or 4 and intercoolers sometime in the next 6 months. Probably in the spring when the winter weather stuff goes away...no need to do it yet I figure with all the nasty stuff on the floor by now.
'12 F10 550i (DGM-II - Dinan Stage 4/Intercoolers & Shockware, H&R Springs, Eisenmann Race Exhaust, Hamman CF rear difuser, Giovanni "Lindo" Graphite 20")
'10 e71 X6 35iDrive SAV (Space Gray) - Gone
'06 e85 Z4 M Roadster (Black Metallic) -Gone
'08 e92 M3 coupe (Sparkling Graphite) -Gone