There are no on-board showers. In the double cabins, each berth has a little sink and the toliets are the end of the car. First class cars are the same, except there's one berth per cabin and it's a bit more spacious.
And all compartments ARE air-conditioned - my memory is that my berth was on the chilly side. In addition, I can only think of 1 or 2 days in the last 4 years when heat would have been an issue. It's July and we're still bundled up - weather warm enough for air conditioning is but a dream here.
Also, I found the service excellent. The staffperson (people) in charge of the train personally checks you in, and they are up far earlier than the passengers (I'd forgotten to change my mobile back from Denmark time so got up an hour early thinking I'd missed my wake up time :o) )
Perhaps you are thinking of a different train or a trip long time ago when the cars and/or company was different. I've never heard complaints about the Sleeper from anyone here.