Hmm, i went through this almost exact thought process late last year.
Bought my CCF from Dengfu. The whole process was pretty slick and the delivery was reasonably fast too.
My LBS built up the bike for me and only ran a couple of small issues.
1) The deraileur hanger screws were put in at a very slight angle and thus had to be slightly machined
2) The seatpost would not go into the frame very deeply, again some minor adjustments (including use of a rubber hammer by me, yes really), solved the issue.
Would i do it again....yes, i now have pretty much my dream bike, for a very reasonable price and as i chose the components myself i feel more like it's "my" bike.
One consideration is that velobuild have removed flyxii as a supplier, this apparently due to the number of quality complaints about the products. Which frame are you considering btw?
Done loads of research into this market also and decided on velobuild...........
I had purchased a bike through velobuild also recently. I had been awaiting an aero frame and bars but there was a delay in the delivery which has now run into chinese new year. This then made order to delivery time close to 2 months so i had a bit of a grumble about it on the forum only to be banned from any more posts!! I had asked how long it would take for delivery before ordering and was told 2-3 weeks for a standard frame, which i then ordered. The constant delays and mis-communications, via email, made me dislike the process hugely.
I had been informed i would get a full refund to then be told it would be after the chinese new year. Long story short i have decided that, yes chinese frames are cheap but if there are ANY issues you will end up with a time consuming pita on your hands. 2 year warranty is all good and well until you have to try and communicate via email with someone who barely speaks the language and then shipping cost is at best shared.
so am looking at
Ribble R872 and planet x N2a frame sets. both good frames and both available for cheaper in china. The after sales though will be much better and i am happy to pay the slight extra for piece of mind.
Some awesome carbon tubs from chinese company called farsports. 50mm carbon tubs at 1100 grams!!! £400 bucks delivered. Tempting.