I am really terrible at calling serves out, especially fast ones.
I will play an entire match thinking I am calling serves accurately on my opponent only to hear my teammate berate me after the match claiming half the serves I played were out.
Occasionally I have had my opponents call their own serve out and I have never argued with them and just let them take a second serve.
Wilson 2012 Pro Tour BLX 16x20, very close to my Dunlop Bio 200 lite with more power. Donnay X-Hybrid a true hidden (and cheap) gem of a hybrid.