What about a product can irritate you?

My biggest are too-coarse or too-fine volume controls and tempermental remotes. The sticker on the CD edges also get to me so I echo Edesilva on that one.

I agree with Edesilva,that little strip of wonder tape on CDs drives me nuts !!!

In relation to TimF's complaint about wandering input selectors, I owned a Jolida integrated that featured a input selector that "wandered." That is, it never seemed to know where the precise setting for any particular input was. It sometimes seemed at rest, then a channel would drop out. I had not experienced that sort of shoddy construction previously (or since).

The "Standby / On" toggle switch on the back of Joule Electra Vamp is located waaaay to close to the right speaker cable binding posts. Oh well. It sounds good, so I deal with it...

Poor quality designs:
Stuff that regularly melts down or bursts into flames without provocation.

Poor quality control:
Loose parts, misaligned controls, crappy finish work, etc.

Poor customer service:
A lot can be forgiven from the above if there is someone at the company of manufacture who gives a hoot that you are not satisfied with their product. Everyone makes mistakes. But, if the company is unresponsive, rude, accusatory or otherwise unaccountable for their shortcomings, I find that totally unacceptable (not to mention irritating.)