I have had leased cars for the last 13 years and all were maintained to the highest standard (ie main dealer). If any part of the car had the slightest of issues I had/have it sorted asap, no questions, whether it be warranty or lease covered (may as well if it's covered and cost free..
) NEVER in 13 years have ANY of my cars been to a back street garage.
Regarding the general condition of the car (ie paint work and interior), that it purely down to the driver and his standards with regards to how much he cares about the car. IMO cars like a M3 or GTI would, in most cases, be a lot better looked after than say a fleet Astra diesel etc. Unless of course you're the 60 year old bloke who had mine for 15 months..