I’ve used them a couple times recently and so far they seem superior to Iteadstudio which couldn’t even align my soldermask accurately… they aligned it to the corner of one of my footprints so it ended up with lopsided clearance.
Also I use the freedfm.com service to check my boards before ordering, also if i need a board really quick I’ll order it from them (Advance Circuits aka 4pcb.com).
So far JLCPCB has been fast, cheap and pretty decent and they didn’t screw up my soldermask. They also include this what seems to be a biodegradable pen in every order I’ve gotten from them so far (perhaps not in the $2 orders). Advanced Circuits usually includes popcorn in their orders… surely this is important information!