Before the Rolleiflex my biggest disapointment was the Nikon F4 that shoots color negative film just fine and if that is what I shot there would be no complaints from me, but it underexposes just enough that slides come out annoyingly dark. What really sucks is that I like the layout of the camera. I should get it serviced, but I'm just too lazy.
Honestly that's a pretty strange "disappointment." It's just a meter adjustment and should be cheap. More to the point, just change the film speed (you can over ride the DX code, I presume - if not set an exposure bias.)
I had a camera whose internal meter consistently underexposed by two stops. I just set the film speed to a speed two stops slower and shot away, for years. I would have hit a limitation with film slower than 64 as I think the speed went down to 16, but I never used anything slower than that. Well come to think of it, I think I did put one roll of Panatomic-X through it, but shot that on manual.
I've never owned a camera that read DX coding. (Yet, I'm sure I will, but I'm more into large format and medium these days. For times when only 35mm will do, my Pentax LX does the job fine.)
Speaking of the LX - while I'm far from disappointed, it does have two serious lacks, one well documented and one that may be unique to me. The well documented one, that I didn't research before buying it, is the lack of exposure memory lock. Even my little Ricoh XR-7 has this. Meter the area you want, push the button to lock it, re-compose. The lack of it on the LX often forces me to manual mode or watching the changing indications and then selecting an appropriate bias when I could shoot much quicker and easier with memory lock. A very weird oversight for such a high grade camera. The other that may be unique to me is that I find the viewfinder indication of manual mode extremely easy to overlook. This causes two problems: first, all too often when I load film I set 1/2000 second to bang off the blanks at the start, then forget to set the darned thing back and waste frames before I notice. The second problem is that when I use manual, if I forget to set it back to auto right away, the same thing happens. Neither of these would happen if I used the camera all the time, but as I said I'm more often shooting with my Yashica Mat or my Linhof these days.
Can't say I'm disappointed with it though. It's a very capable and well constructed camera.