I really like the new A Class and the cabin is superb. Two negatives for me are lack of a space saver and shape of the seats (I looked at a 250 AMG Line). With the amount of miles I do, often rural and at night, a space saver is a must (they could have at least made room for one even if not standard). I also couldn't get comfortable in the seats - it feels to me that the fixed headrest tilts forward too much.
As an aside, I didn't think much of Merc sales staff - weren't that bothered. Maybe they only show interest if you're buying an E Class.