A quick report from the SAW domestic lounge: it is located in a separate "terminal"; after check-in, you leave the terminal, go down one floor to the arrivals level, and look for a shuttle with a sign that says "TK VIP lounge". It's a short ride to the lounge. Then, as in IST, there are two separate spaces, one for Elite+ and J and one for all the others. Surprisingly, both had the same catering but the "lower" lounge (left) was more spacious and better air-conditioned.
There's really nothing of interest there: very limited catering (sandwiches, soup, water, tea/coffee and some cookies), not much to do (but a nice view of the tarmac), comfortable seating. Flights are called (in Turkish only
and they bus you to your aircraft.
I suppose it is possible to check in at the lounge (in other words, one may possibly show up there rather than to the main terminal) but I'm not sure. If you are already checked in and don't have checked luggage, it does give a feeling of "a separate VIP terminal". Poor man's LH First Terminal...
Shuly