I got a Samsung S4, have had it for a few weeks. Also had an HTC One. The S4 lags at times in the UI (app's "Drawer" and settings particularly). HTC never lagged in the sense department.
Removing the animations helped tons on the S4.
To the OP: I think you are expecting a little too much and blaming things when there is no one to blame. Anyone who says "get what you pay for" should probably look at what their saying. YOU ARE getting what you are paying for. Saying you want what you pay for implies there is a substantial data point indicating what you are receiving is NOT the norm for that product which is simply not true when HTC has already stated it is normal for a gap to show between speaker grill and the plastic.
I used to collect knives, watches, and swords and spent a good chunk of money. Always obsessing over the smallest details until I realized even after you spent $1,000 for a knife, more for a sword, and even more for a watch you kind of realize even in the mid to high end: It's not perfect. Period.
Enjoy the phone for what it is. If the gap is truly something you can't deal with, then you know what that is YOUR right as a consumer not to buy the phone however understand nothing is perfect and no matter how much money you throw into the pool you won't get perfection.
The best you can do is try to understand and cope with that everyone does the BEST they can. It truly helps one's perspective.