I will counter with my long-haul TK experience, which has been absoultely excellent--and that's 3 on ORD-IST in Y (2x) and IST-ORD in Y (1x), along with IST-ORD in F (1x).
Short haul, it's a bit less positive--I did IST-BEY-IST once, and with the short flight, less fancy food, and brusqueness of the staff, I can't say they outshine anyone.
But for longhaul, it's a different story: In Y, I've flown all three planes: 77W, 330, 343. All have 34"+ of pitch, except the 77W, which has less--but also has the newly designed seats that slide forward--so in TK Y, you'll NEVER have the seat in front of you touching your knees.
Catering in Y is the best I've had in years: fresh and tasty. I like TK's cherry juice too. Alcohol is free. They also use Do&Co, though obviously a D&C Y class product.
IFE is AVOD, though this is a downfall--they don't change it so often. But AVOD is nice to have.
Staff is just not very well trained, so the level of service really depends on the crew you get: lowest is very low (but the highest is very high). Language skills (other than Turkish! ) are moderate to poor, though a few have excellent English.

Ground service is pretty poor, though (while the lounge at IST gets crowded, the food offerings are decent, there are good showers, too)--but in Y, you're on your own, and staff at outstations can be clueless, though the ORD staff doesn't seem to be outsourced--I think they're TK.
My F class experience ex-IST was truly amazing: Limo from my (3*) hotel, separate immigration line, small lounge with meal service, "car" to the gate with personal escort the whole time (from when the Limo arrives at your hotel till when you arrive in ORD, when someone greets you at the plane door-- and brings you through to ensure your connecting flights are ok).

So I would highly recommend TK in terms of catering and also hard product; they just seem to me to be a very-quickly-expanding airline that hasn't the time to train its FAs and ground staff to be consistent.