An update on the car since I have now had it for about 7 months.
Power:
What can I say about it? Well the power and performance is addictive. It is fast, very fast. In a straight line. I don't think much would hang with it due to the way the power is delivered. Just tickling the throttle results in quick acceleration. 30-70mph happens in no time at all. It sounds good as well, especially when just lightly accelerating rather than foot to the floor. The engine is real masterpiece and feels bulletproof. I could throw the kitchen sink at it and would take it without fuss that belies its 139k miles. The low point for me is th gearbox. I know it is strong, but it is an automatic, and saps the fun out of it when making progress. I have tried using the manual shift buttons but they aren't the same as changing down when slowing and using the engine breaking. When pressing on in a straight line the gear changes are ok, but around town in normal driving the changes are slow. It breaks traction very easily and would benefit from an LSD. Why Mercedes do not fit LSD's as standard to the AMG range is baffling.
The handling:
Or lack of. Throwing the car into a corner does not instill me with too much confidence. In comfort mode the suspension is way too soft, in Sport 1 not difference and Sport 2 just to makes the suspension superhard over bumps and pot holes, but doesn't really aid the handling. It is a straight line machine and does this well, but it is not a B-Road stormer. I would even say that a sweeping A-Road is also not really its forte.
The interior:
Taxi!!!! It feels well put together but at the same time feels a little cheap. I guess it may be because I am used to button placement on other cars, but I find the single stalk annoying and some of the button placements odd. I have would have had the Climite Control buttons lower and had the stereo screen higher. The dash clocks are nice, the mix of Analogue for rev counter and speedo and digital for fuel level / water temp is quite good as it makes it easier to have a big speedo / rev counter. The information display has plenty of options which is great if you like that sort of thing. I tend to just leave it on range left.
The seats are suportive, not too firm. I like the dynamic seat bolsters. The massage function is useless. I would have liked the air cooled seats but it wasn't a deal breaker. The rear seats are OK. I haven't spent a lot of time in them but the back feels a little firm. This may be because it has the split / fold rear seats, a feature which is so useful and something I have missed on my last few cars. There are some squeaks and rattles, especially the panoramic roof, but this is a well known thing. I do like the roof, it adds something to the car, though I'd be just as happy without as I never use it / never have the interior covers open.
Audio:
Not a lot to say - best stereo in a car that I have ever had.
The exterior:
It is a handsome looking car IMO. Not as nice to look at as my old E39 M5 though. It is well proportioned and it does look agressive from the front and rear, but not overly aggressive. The 4 pipes at rear are spot on. It does sit too high IMO and could do with being a little lower from the factory but that can be sorted in various ways.
Running costs:
It hasn't been too bad, mainly fuel and the odd oil top up (these engines do use a little oil). It has been reliable so no big bills. I've replaced the engine and gearbox mounts and that is pretty much all I have had to do to the car.
The driving experience:
I have never felt like I drive this car, more so that I just pilot it. When I sit in the drivers seat it feels like I sit "on" the car rather than "in" the car. It is difficult to explain but I am sure people reading this will have experienced it at some point in other cars. It is fast, blends in, isn't really that shouty, doesn't really stand out in the car park which I like. People do know what it is and people have spoken to me when I have parked up / they have seen it outside my house and I've been outside and talked to me about it. It is sometimes fun (and very childish) to bury the throttle from low speed and light the tires up (despite the lack of LSD it can over power the open diff and spin both wheels).
In conclusion:
It is a good car. Not a great car but a very good and competent car. Do I regret buying it? No. Would I buy another? Yes, but with less miles or a CLS55. It is a bit of a one trick pony really. It goes fast in a straight line. Obviously it is a comfortable place to be on long journeys and can get you were you want to be quickly. It is effortless. Overtakes are easy, motorway travel is easy and town driving is easy thanks to the auto box. But it isn't a fun car. Sure I still sometimes laugh and giggle when I mash the throttle and it goes quickly, but I do miss the involvement I had in my old M5. The E55 doesn't make you feel part of the process, my old M5 did. Sure the E55 is so much quicker than my M5, has better audio and less prone to rust, but the M5 is better looking, more fun, isn't slow, has a better interior IMO and as a drivers car is just a lot better. Sure I wish the M5 had better audio and a few of the features that the E55 had, but as something to drive for fun and get more of buzz from, the M5 beats the E55 by a country mile.
Whats next?:
Well, I'll be selling the E55 soon and then I have to make a choice between a few cars. I am considering an E9x M3 (E90 is my preference, it just looks a lot nicer IMO), an Audi S4 B8 (not as dynamic as the M3) or looking for a good E39 M5 in something other than Carbon Black and supercharging it. I still want an F10 M5, but I think I could maybe live without one for a while with a supercharged E39.
TL;DR - Bought W211 E55, decided it isn't as good dynamically as E39 M5, looking to go back to something more dynamic.