We do have a lot of experience, my graveyard of phones can prove that

Yealink, 110% of the way. They make a phone that is hot, really works and responds, price point is excellent.
T41P, T42G, T46G and the T48G, are awesome phones on every venue.
Grandstream, Snom, and Polycom, we dumped a couple of years ago. All for different reasons, known of which was cost.
Just my 2C
Walter