i dont really regret these as much as i maybe would have gotten a different gun if i could go back and do it over:
my beretta u22. stock front sight is really blurry for me (almost any black/black handgun sights are for me) and there are no after market options that i know of. also went shooting ourdoors one day, some sand got in the trigger somewhere when dust picked up and the trigger break is a bit gritty now. i can't open the thing to clean it out. lastly the grip is a bit small for me but overall i still enjoy shooting it a lot.
maybe my 7.62x39 saiga. it is probably my most "fun" gun, but i could have got an arsenal saiga for about the same price with everything already converted vs all the time i took to do it myself. but again, not really a regret, b/c learned way more about the rifle this way than i would have buying an arsenal. also found little things i like and don't like on ak types by experimenting on my saiga.