Second Opinion on Tiling
This appears to be very shoddy workmanship. I can't tell a lot about how plumb the walls may or may not be but the wallboard has to be done properly in order to get good results once the tile is applied. However, it doesn't appear the tiler is very knowledgeable or skilled with properly installing tile. He/she should be using spacers between all of those tiles in order to control the gap between tiles. That's tiling 101.
It's always a good idea for jobs of this type to get referrals. Don't just accept the lowest bid.
IMO - I think the job needs to be redone.