Been using PCBWay since last year, I've ordered 10+ jobs from them, totalling several hundred boards. No complaints here. The only downside is the DHL shipping... expensive. But at least you get a tracking # and you pretty much receive it 2-3 days after they ship it out. I also like with PCBWay, you can do combined shipping and that's one way of saving money.
I used to use PCBCart, but their prices have slowly gone up over the years, and I HATE the setup fees for 1st time ordering of the board, and possibly new setup fees if dramatic revisions done to the board. If you're spinning and doing lots of revisions to the board, I just HATE those setup fees. So I left them, but used them for a good maybe 5 years. Their quality also seems to have gone over the years, vs the first year I tried them. A few times, I had to complain and they had to redo the boards, as the hole sizes turn up too small.
I tried SeedStudio, but their ordering process isn't straightforward and easy as PCBWay.