Many of the things people are complaining about are not because they are rules purists, but because some systems uses PHB rules, and other systems use Larian's modified rules, and that has a clear impact on the game's balance.
Precisely this. I personally prefer the rules/systems in 5E to those of OS, but rather than using one system or the other we've got a mix of the two, and there are areas (such as the changes to certain cantrips) where that either doesn't work very well or mangles the original intent of a rule to the point where it does something substantially different.
Part of the point I was trying to make earlier is that the inclusion - nay, prevalance - of OS things like surfaces means the 5E rules have had to be drastically changed in some ways, and I don't believe that's to the benefit of the game. If they insist on surfaces being part of the game, the surface mechanics should be changed to accommodate 5E instead, as this is a D&D game.
