I would also like to ask:
How would you, as a DM, feel if a player was upset that you weren't using a certain common houserule?
And how would you feel as a player if a DM doesn't use a houserule that you were used to?
Depends on the rule, really.
Potion as bonus action: without this, potions are a lot less useful, so as a dm I'll drop fewer and as a player I won't seek them out. I usually play with this, I think it makes the game better.
Surprise rounds: actual ambushes aren't really common enough for me to care all that much how the dm handles it. If the players understand RAW I'll run it that way, if they don't a surprise round is easier to explain.
I usually enforce line of effect as a dm because it makes more sense then purely visual limits and wouldn't try to game it as a player unless the situation were desperate. I'd only care on a case-by-case basis.
Auto success/failure: it really only impacts saving throws, and it's common enough that I can go either way. I do always specifically ask about this one as a player. It only affects certain very specific builds in term of how I play the game. (Attacks already work this way, skills sort-of de facto do in that dms seem to rarely call for rolls you can't pass unless it's a group check.)
Everyone speaks common: because the alternative is clunky.
Flanking: I don't like it. It makes a lot of subclass-defining features redundant with "just moving." If it's in play I'll still play, but I'll play different characters. As a dm it's a no.