Worst is when the disappointing stuff are things you don't think of until you use it. Like my convection toaster oven is the best oven I've ever had but I hate it because the UI is awful. It's all preset based with presets I never use when there's only like 4 options to adjust, so I need to figure out which preset is closest to what I want then adjust it from there because none of the presets are good for anything without adjust them.

It makes buying things a bit of an ordeal, but on the other hand, I can't say I really dislike usually deciding to not buy something until I can do more research on it.

It also means that getting me a gift that would be something I'd really care about is going to be very difficult if you want it to be a surprise. I am picky as hell and hate badly designed shit, which includes most things. So I'll appreciate the thought and effort of a gift but can also resent that either this thing that I didn't choose is now a part of my life or I'll have to feel bad and ungrateful for getting a better version that won't annoy me each time I use it.