I recently had the Dinan Stage 3 engine tuning software installed on my 550i, and it's turned my car into a beast! From 3K RPM onward, it's a completely different vehicle by way of a tremendous (and linear) surge of power and acceleration.
Had the engine software upgraded in October shortly after the installation of Dinan's performance exhaust, and have had no issues whatsoever with increased idle roughness nor trouble lights. Got the Dinan spring set / supplemental ride quality & handling kit / EDC software reprogramed (Dinan's "shockware") last week, and again, am loving the transformation of my F10 at each step of the process. So much so, that I ordered up their low compliance rear control arms yesterday to further tighten up the rear suspension (I upgraded to 20" wheels, and in combination with the extra power, it can get a little squirrely at the ass end with the OEM rubber bushings when I aggressively toe into the accelerator).
Are there more cost-effective options than Dinan out there? Absolutely. However, I have no regrets over any of their performance upgrades, and would do each and every one of them once again in a heartbeat if need be. Their customer service has been awesome, and it became very clear when I began my research into their product line that they engineer and test the sh*t out of their innovations (all in-house) before releasing to market. Plus, they stand behind their product 100% with their warranty, and the fact that BMW corporate has endorsed their tuning capabilities (with a nationwide distribution network on showroom floors) meant a lot to me.
I get that their stuff may not be for everybody, and that there doesn't seem to be too many folks on this forum touting the Dinan line of performance products. Thus, I offer my two cents and hope it helps others contemplating aftermarket upgrades and researching vendors for their F10 mods.
