Super Uwe - Hi there! We've just clocked up around 4000 miles now, and we are still very happy with the 500L.
I'll try to answer your questions as best I can!
Liveliness is rather difficult to categorise. At times it can feel very spritely- the short first gears gets you off the line quickly, but you'll need to grab second, fast! Around town, the car feels great, and can easily cope with typical town driving. Economy obviously depends on how bad the traffic is, and your driving style, but I get around 34. The suspension is very compliant taking road irregularities and potholes very well, with no bangs or crashes!
Motorways are taken with ease. Cruising in 6th is relaxed, with even a little in reserve for overtaking, you'll be taking 5th or even 4th if you need to gather speed more quickly. Average economy at realistic motorway speeds seem to be around 42. Noise is generally subdued in the cabin, apart from when pushing on in 4th gear with your foot down! There is some wind noise, but no worse than I have experienced in other more expensive vehicles. For such a high car, crosswinds are handled well.
'A' roads seem to give the best in terms of performance - the lower average speed seems to have a big impact making 45+ perfectly possible. Corners a fine without too much body role, but some common sense is needed if you have your beloved pooch in the back - and on that note, our dog loves the elevated view from the back!
I think a couple of odd decisions were made with regards to the gear ratios. 4th, 5th and 6th are very close, making 5th redundant much of the time. There's quite a gap between 3rd and 4th that could be closed by making 1st longer and moving 2nd and 3rd up a bit. I don't want to make too big a thing over this though, so it takes only a short while to get used to this arrangement!
Finally - no rattles or creaks! In fact I'm very pleased with the general build of the car. The paintwork is pristine, and polishes-up nicely. The glass roof is a bit of a stretch to clean - being over 6ft helps here!
If you have any more questions, or if I missed anything, please get back to me.
Simon...