the niche is actually a nice job. with those small glass tiles, thinset always oozes through. all he has to do is scrape it down w/a razor blade. they aren't meant to look perfectly even and flat. they are to take on more of a handmade look. Once it's grouted it will be fine. your bottles will hide most of it anyway. If I had to criticize something on the niche, it would be the upper gap w/large tile. Seems like those grout lines are a bit larger than the others.

as for the tiles on the outside edge, that's common. He might have used a thicker edging piece. I suspect some caulk and paint will fix that.

the reason the grout lines aren't level all the way down, is most likely your wall is out of plumb, causing the tiles out of plumb. the very top edging piece should have been pushed to the left a bit

what else don't you like?

Any "Pro" worth his salt would have checked the walls for plumb & level before undertaking the job. He would have explained why it was worth the few hundred dollars to have him "float" the surface. I don't see any waterproof membrane when looking into the grout joints. A cement backer board does not constitute waterproofing.

"He said he tested a lot of products over the years and uses
Wonderboard--but perhaps that doesn't really constitute waterproofing."

Correct.

Wonderboard is a tile backer board. It's cement based. Wonderboard itself is impervious to damage from water, but by itself it provides no protection to your house from water. When saturated, water can pass through Wonderboard with the Wonderboard itself not being damaged.

Some sort of waterproofing is uaually used in conjunction with the Wonderboard. It can be a drainage plane behind the wonderboard; 6-mil poly plastic, or even tar paper. Or on the face of the wonderboard, a surface applied membrane like Hydroban or RedGard liquid, or one of the sheet membranes could be applied.

"...not sure what you mean by a drainage plane."

"Drainage plane", something behind the wonderboard to stop water from infiltrating in to the wood framing bays of your house. Should moisture get through the grout and saturate the cement board, it will be caught by the 6-mil poly barrier (drainage plane, or moisture barrier, etc) that is generally stapled to the wall studs before the cement board is installed.

After a typical wetting cycle, during the drying cycle the moisture captured by the plastic sheeting will evaporate back out through the grout.

Here's a random google photo simply to show cement board installed over poly sheeting.

That would be a concern of mine. Once you start ripping sections out, it’s very difficult not to damage what’s underneath.....then what happens to your waterproofing? My builder just had the tile guys rip out one of our showers down to the studs. There were some crooked tiles, and it was impossible to remove them without causing gouges in the waterproofing. It was his decision to just rip the entire thing out (at his expense).

***Just needed to add that all the trim around my niches are mitered....even the thin pencil molding (including the one they’re tearing out :) ).

I would have used a bullnose finished edge tile to go inside the niches wall mitered. Same thing on the outside corners. I would also be worried about the waterproofing barrier.

not all tile offers bullnose. I don't care about the type of trim, but I do think he should have given you options when he found that the walls weren't plumb. however, this will probably look more acceptable once the caulk and paint fill in that gap. it's the dollops of thinset that are drawing your eye.