personally i wouldn't buy one of those brands though, as they just don't have the runs on the board. the frame is the most important part, and i'd rather stick with a known quantity.
Reality is though some of us look for a bargain, and when it comes to just wanting a bike to get and keep fit on, something that is a step up from a supermarket chain bike may suffice(?) In my case looking at an online purchase was convenient at the time as I was "living in the sticks". In 2012 I purchased a Hasa R2, happy that it was made in Taiwan and came with a Tiagra groupset, figuring it would do me as a first bike (after 3 decades of distance running to keep fit I decided I needed something a little easier on my aging joints). After sorting out a problem with some dodgy rear wheel spokes, I have used it consistently since, clocking up around 15,000 km on it with no issues other than usual maintenance (new chain, just replaced brake and gear cables). I can't complain about that! I also bought a Cell 105 a year later as a second bike, but actually prefer the Hasa to ride.
Found this review on some budget bikes interesting.
http://www.bikeradar.com/au/road/gear/article/best-direct-buy-budget-road-bikes-40753/Buying the Fuji was a step up again from my Hasa and Cell, noticeably a little faster and "smoother" to ride. I was willing to buy a carbon frame bike and spend a bit more, but considered the Fuji a good buy, too good to knock back at the time.
I still rotate rides on all 3 bikes, although these days prefer the Fuji (understandably).