Have also been researching Tayana 55s. Agree tognews is not a very good source of information for the 55s, or even the 52s. I am guessing it's because there are so few.
I'd recommend finding your local "new" tayana dealer, and getting an inspector recommendation from them. Maybe someone who inspected these boats when they came in as new, or has inspected them over their lifetime. My local broker was able to make such a recommendation. FWIW they are still making the T55 center cockpit, though are pushing the T55/58 Deck Salon which seems to be a cosmetic redesign only and the original hull is essentially the same.
Not a specific Tayana thing, but everyone brings up concerns on the teak decks due to the way they were constructed. You'd want to find out if they were redone, and if not if there are problems. Also whether they will be due for being redone again. This is common to other boats though, so I think any inspector will catch this.
It seems that they were well built and that any issues to look for are no different than that of any other aging sailboat. Rigging, sails, hardware, engine, all should have been serviced, replaced, etc at the right times. I'm basing this assessment on reading what people have replaced on their boats.
A knowleadgable inspector familiar with these boats though will have seen all kinds of things I'm sure.
Please share if you find out about any issues though!