Having used these services, here's some advice/traps for young players:
1) Silkscreen isn't that important unless you're going into production - and are you really going to stiff your customers with crappy boards? The only other place it might matter is if you're dealing with particularly sensitive layouts where you don't want gunge on your traces, but again - why are you using a $10 manufacturer?
2) Etch quality is normally fine with these boards, pushing the fab minimums is asking for trouble, but standard 6/8mil is never normally a problem.
3) Shipping is a lottery, sometimes stuff arrives very fast, sometimes it doesn't, that's just HK mail.
4) Drill quality is where you might start to get worried because if the holes are sloppy, you might end up with messed up vias or holes in traces where they shouldn't be. (see https://www.sparkfun.com/tutorials/115) This is something that the cheaper houses tend to fall over on, but you can get round this by making the via rings larger to allow for their mistakes.
5) Panelising is an interesting case here, as someone mentioned. DirtyPCB specifically mentions V-cuts in the fab specification so presumably they're allowed. There's no good reason why any middle-man should prevent you from making a design if the fab wouldn't make it for the same price.
6) Cost per board - there's a fixed cost here which seems to imply that if possible and allowed, you should panelise your boards or at least put multiple copies into a single 5x5 or 10x10 shape.
If you want an alternative, look at OSHPark, http://oshpark.com. They offer $1/sqin for 3 boards shipped anywhere - this scales to 9 boards for $12 so fairly similar to dirty PCB and often cheaper because often you only want one or two revisions of a prototype board.
The quality is excellent, you get ENIG (gold tinned) plating and they're made in the US which should mean fast shipping. For us in Europe, shipping is still a gamble. For more advanced designs you can get 4 layer boards and there are cheaper options for large orders. You can only get purple boards, which look cool, but aren't for everyone.
Critically the price is per square inch rounded down to the hundredths or thousandths. So if I want to make an LED breakout board that's only 0.5 square inches, I only pay $0.50 for 3 (and I've done this).
There's also BatchPCB, but as they lost my order and are no longer price competitive I'd have to say they're not worth it any more.
Panelising is interesting... Most forbid it, our house calls and asks if it's ok to panelize small boards :) Imagine that! They charge $2 for it, but whatever. We did Hacker Camp Shenzhen this week and made everyone's PCBs as part of the camp. The board house panelized anything that would fit!
Now, quality fade may set in. It might get crappy over time... however we're prepared! It's dirty boards after all!
I said so below too, but OSH Park really is $5 per square inch, for three copies. Not $1. They are awesome, but not as cheap as you seem to be thinking.
Interesting, what's oshpark's real-world turnaround time like for 4-layer boards? I've used batchpcb before, but I always had to wait a few weeks for a 4-layer panel to go out since most people use 2 layers.
1) Silkscreen isn't that important unless you're going into production - and are you really going to stiff your customers with crappy boards? The only other place it might matter is if you're dealing with particularly sensitive layouts where you don't want gunge on your traces, but again - why are you using a $10 manufacturer?
2) Etch quality is normally fine with these boards, pushing the fab minimums is asking for trouble, but standard 6/8mil is never normally a problem.
3) Shipping is a lottery, sometimes stuff arrives very fast, sometimes it doesn't, that's just HK mail.
4) Drill quality is where you might start to get worried because if the holes are sloppy, you might end up with messed up vias or holes in traces where they shouldn't be. (see https://www.sparkfun.com/tutorials/115) This is something that the cheaper houses tend to fall over on, but you can get round this by making the via rings larger to allow for their mistakes.
5) Panelising is an interesting case here, as someone mentioned. DirtyPCB specifically mentions V-cuts in the fab specification so presumably they're allowed. There's no good reason why any middle-man should prevent you from making a design if the fab wouldn't make it for the same price.
6) Cost per board - there's a fixed cost here which seems to imply that if possible and allowed, you should panelise your boards or at least put multiple copies into a single 5x5 or 10x10 shape.
If you want an alternative, look at OSHPark, http://oshpark.com. They offer $1/sqin for 3 boards shipped anywhere - this scales to 9 boards for $12 so fairly similar to dirty PCB and often cheaper because often you only want one or two revisions of a prototype board.
The quality is excellent, you get ENIG (gold tinned) plating and they're made in the US which should mean fast shipping. For us in Europe, shipping is still a gamble. For more advanced designs you can get 4 layer boards and there are cheaper options for large orders. You can only get purple boards, which look cool, but aren't for everyone.
Critically the price is per square inch rounded down to the hundredths or thousandths. So if I want to make an LED breakout board that's only 0.5 square inches, I only pay $0.50 for 3 (and I've done this).
There's also BatchPCB, but as they lost my order and are no longer price competitive I'd have to say they're not worth it any more.