Like most of us that have been buying these watches for a few years, I have had a fair amount of dissapointing pieces. However I think a few of those previously mentioned are the prime dissapointments for me as well.
1. IWC GST Chrono - Like Ubi, the case IMO is way disproportionate. 40mm case - but it felt like the thing was 3 inches thick. So nice to look at, but not fun to wear.
2. Cartier Santos 100. I didn't like the strap, and tried to change it, to no avail, and after wearing it once or twice, sits in the box.
3. As much as I like many of the PAM models - the 196 is the biggest disappointment of all. Bought it as it was released - paid 340.00 with a cheap strap, bought a sourced SS PAM bracelet for 125.00 (now of course they come with the SS bracelet) - 7750 problems immediately - won't reset correctly, etc. I can never sell it, in its present state. Haven't bought any of the newer PAM models since.
Most impressive rep? The look and feel (weight and fit) of the 2006 TAG LINK chrono is as nice a rep as I have ever purchased.