Still on TK/Istanbul
I have also used TK via Istanbul to a couple of lesser African/ Mid East destinations in recent years, and have no complaints.
I think the problem they have is that TK has expanded very rapidly, whereas IST has not; I have experienced tedious holding which turned an ontime flight into a delayed arrival, and a hectic rush for the connection home, which I just made but my bag did not.
There is of course a new, larger, Istanbul airport due to open fairly soon, after which TKs hub may begin to resemble AMS or DXB rather than LHR; in the meantime I would echo the advice to ensure a generous transit time of at least 2-3 hrs when using TK via IST.