Just used SEED studios as well as Elecrow for the first time for both..
was trying to compare to iTead/iMall... when I need an odd size they didnt offer in a small batch pcb (5cm x 10cm)
SEED had that size in small batches of 10.. cheaper than i could get from iTead for only 5 pcbs..
I had some other pcbs I needed to order.. in my usually 5cm x 5cm sizes..... so i decided to use Elecrow, because of their posting here.... and because they give you FREE color pcb's..
I can say that all 3 are more or less the same as far as board quality goes.. Im not sure if it OSH Park quality..but I think they are good... GREAT even for the price.
iTead told me they would have met the SEEED price if I was a better customer (which up until now, i had only ever used itead before.. so go figure?)
SEEED had decent shipping..
Elecrow has free color, good communication on the status of your order (and send pics of your pcb's when done/shipping)
I will probably stick with Elecrow for now, as its more or less the same as iTead, they seem to want your business, and color is free.. (which i really enjoy)..