My dad got an f10 550 about 8 months ago and I've had a few opportuntiies to drive it now.
-Regarding idrive- yes there are some quirks but overall I stlll think its the best "infotainment" system in the business. And that includes Tesla's gigantic touch screen. The voice recognition on the nav is surprisingly good-- you can say the entire address in one shot and it gets it right about 99% of the time. Better than Siri i'd say. Not sure exactly why you can't switch out of perspective mode but not sure if i understand the problem exactly. My only remaining pet peeve with it are that they should give you more options for the split screen-- but the HUD that's now available makes up for that. And i've never seen it freeze up or behave inconsistently.
-Agree the trans selector is change for change sake and kind of annoying (especially when it tells you that you have to press the buttons on the side-- if its smart enough to give the error why not just eliminate the buttons?). That being said, after the second time I drove it I didn't mind it and kind of got into the geek factor of it. Only thing I don't like now is that the action feels kind of cheap/plasticky comapred to the older steptronic gearshift that was mechanically connected. My dad did mention however that on 2 occasions the car wouldn't shift out of park. The old "reboot" trick solved it, of course, but its no surprise that a BMW e-shfiter would malfunction. They'll get it right in another 5 years.
-Overall, the interior design, build quality and materials are probably one of BMW's best ever efforts. Not sure what seats your loaner has but his 550 has the "comfort seats". Best seats i've ever sat in. I could live in those seats.
-His car also has the "self closing" doors. Yeah, its kind of silly but I found them cool all the same. Found myself opening and closing the doors a few times (like a little kid) just to watch the doors do their thing. My wife (who cares less about cars) got really into it too.
-Agree- the F10 is a boat. The F10 doesn't come standard with adjustable dampers, but they all come with the "drive mode selector". WIthout the adjustbale dampers, it just controls steering weight and transmission shift points. That could be why you didn't feel a change? Overall though its a very easy, comfortable car to drive. And it will take pretty much any corner at speed without compalint (though you get the sense it doesn't really want to).
-The torque of the turbo V8 is addictive and grin-inducing. It catches you off guard too cause the rest of the car is so soft and luxo.
-Not a fan of the direct-injection "ticking" you can hear outside the car, and my dad's car makes some diffefential whine that you can hear inside.
-Not only is the car long and wide, its also quite tall. Didn't appreciate how much so till I saw it parked next to his old e38 (which is about hte same size in other dimensions). I cannot even imagine driving an F01 7 series. And while its one of BMW's better current designs, it still pales next to the sleek e38.
-BMW needs to do a better job on panel gaps-- they're too wide.
-The HK stereo on it doesn't sound as good as the one in my e92.
-For some reason, the shape and size of the side mirrors bugs me. They look cheap and they're smaller than my old e46s.
Overall, I think its the best buy in the luxury sedan market-- but that doesn't mean i want one. And I cannot even imagine owning one of these out of warrnty- the opportunities for expesnvie failures are everywhere. The even larger, heavier, buggier and more expensive Tesla Model S would be my choice. But I think that's the subject of another thread...