I just bought two 4.3" qHD midrange chinese smartphones based on the mkt 6575 platform; as Im writing a review for a local site, I thought Id let you know my experience here as well.
What I got:
x310e with android 4.0."9"http://elifekey.en.alibaba.com/product/576406221-213148745/X310E_mtk6575_android_4_0_Wifi_GPS_3G_smartphone.html
Star B79, but with android 2.3.6http://www.uuelf.com/B79-Android-40-3G-Smartphone-43-inch-Dual-SIM-WCDMAGSM-WiFi-GPS-Capacitive-Touch-Screen-Black.html
Both of these phones can be found online for ~$180. These are essentially the same phones underneath, and almost identical to the somewhat more expensive but better known and supported Zopo ZP100. They are all based on on the 1GHz mkt6575, 512Mb RAM, 4GB ROM, have dual sim/dual standby, 960x540 display, 5MP autofocus camera, dual flash, 5 point multitouch etc. Most of the things you would expect to see on a highend smartphone, except there is no NFC, and the cpu is only single core. I would have liked to see 1GB Ram too.
Built quality is not what I expected from a Chinese knock off phone. Especially the B79 actually looks better than any samsung galaxy Ive ever held, including the S3. Its really nicely made, thin bezel, sturdy, nice looking rubberish finish on the back, not the cheap looking plastic of many actual highend phones. The screen is not mounted at an angle and the back cover fits perfectly. Im impressed with both, and most by the B79.
Performance wise, these phones also perform way above my expectation. Specs would suggest performance somewhere between a galaxy S and galaxy SII as they are built around the mkt6575 (single core 1GHz cortex A9+SGX531), compared to a Galaxy S1 which has a 1GHz single core cortex A8 and an S2 which has a dualcore cortex A9. for most apps that dont make use of multiple cores anyway, this phone should perform pretty much like an S2. In practice they are simply very, very fast indeed. Ive never seen android boot this fast, browsing works without a hitch, demanding games like Need for Speed, or Samurai II work flawlessly, no stutter, no lag. Impressive, particularly considering the price and the fact these phones have quite high resolutions.
Display quality is also better than I expected. AFAICT, they sport the same LCD. Images are very crisp (qHD really rocks), viewing angles and sunlight readability are reasonable, contrast is good but the colors seem perhaps a little washed out compared to some AMOLED screens Ive seen. Still, its a joy to look at.
Touch screen is a mixed bag. On the B79 it works perfectly and is extremely responsive. Seriously, an iphone is no better. The x310e however, only works well when holding it in your hand. When you put it in a cradle or on a flat surface, it usually doesnt work at all. And i mean, nothing. You cant even unlock it. Just touching the phone with another hand makes it work again, well, usually. Weird. Not sure whats causing that, but its pretty annoying. Even when holding, the x310e doesnt seem quite as responsive as the B79, but that may be due to software.
The dual sim works a treat and is a godsend for me. Both sims work simultaneously, you dont have to switch. Both can support 3G and you can manually select or predefine which sim to use for what.
Camera's are okay too. Not fantastic, but 5MP (often advertised as 8MP, but thats just interpolation) and autofocus do what you would expect, but not more than that. It wont replace my SLR anytime soon, but Ive seen far worse shooters. The dual flash is pretty good though, quite powerful for a led flash. Front camera works fine in Skype.
Call and audio quality are very good. More than loud enough, crisp and with a headset listening to music, I found the audio quality beyond criticism.
GPS reception is definitely a weak point on both phones. Perhaps even more on the B79. I found them acceptably fast to acquire a signal, but the lock is easily lost when driving, or inside a building its almost impossible to get a signal. Its usable, but only barely. I knew this when I ordered them, its a known weakness, but Im still a little disappointed its actually true
Wifi reception is ok, not superb either. But its performance is very good, downloads are actually faster than on my laptop! Installing apps through Google Play store is almost shockingly fast.
Battery life is again decent, but not stellar. As you might expect with a 4.3" phone, if you use it heavily, particularly when gaming, it wont last a day. But with light use you might eek 2 days out of it. Nice touch is that you get 2 batteries with both of these phones, though without external charger to charge the second battery, thats of limited use.
Then there is the software. Both phones firmware have a few quirks. The internal memory (4GB) is split between internal and "sdcard" while the actual sdcard gets mounted as sdcard2. Few apps can use that. You can use the sdcard to store music or movies, but dont expect to install apps on it. There are alternative ROMs out there that fix this, but I havent tried them yet.
My x310e came with android "4.0.9", which doesnt exist. Its just 4.0.3 that they ruined. Its buggy, it fakes information (it will report 2GHz clock speed and 1GB Ram, in reality its half that), its more sluggish than it should be. On XDA forums some people have flashed it to 4.0.3 ROM from zopo with promising results, it cures most of the bugs, apparently fixes the touchscreen, and makes it faster. I will have to try that later, but for now, if you want to buy this phone, make sure it either comes with 4.0.3 or 2.3.6.
My B79 came with Android 2.3.6, and though it lacks some of the features of android 4, IMO its the better choice for now. By installing some custom launchers and other utilities you get 98% of the looks and functionality of android 4.0 without the problems. The phone is upgradable to android 4, but the place I bought mine from recommended against it for now, and I have to agree. I will wait for some custom ROMs to mature first. Word of warning; when I reset my phone to factory defaults, I got a Chinese interface.
TL;DR. out of the box, particularly the B79 with android 2.3.6 is actually a great phone for a fantastic price. Heck, its cheaper than most second hand galaxy S1s around here, and its by far the superior phone. The only real let down is poor GPS reception. The x310e with the software I got, I would only recommend to people who dont mind getting their hands dirty with custom ROMs.
If you want a cheap 4.3" phone with android 4.0 preinstalled, the zopo ZP100 might be the phone to get instead of either of these two. Its about $30 more expensive but zopo actually appears to do a decent job of making android work on their phones. I just didnt like the design of it