I own a batch 3 S:flo2 and I am a Chinese living in Hong Kong.
I must tell the truth that MY very S:flo2 sounds better than all the portable cassette players, portable CD/MD players, MP3 players I have owned in the past. It is especially true for its line out.
BUT, and it is a big BUT, you have to know that not all S:flo2/T51 are created equal and sound the same.
There are user cases in the Chinese MP3/4 forums, and in the head-fi S:flo3 threads reporting:
1. One fellow in the Chinese forum saying he owns 3 T51 and each sounds differently.
2. Many users reports that they cannot start up the players without plugging in the USB cables.
3. Screen quality issues (color bands)
4. Battery life get shorten significantly after a few months of daily use.
So what do all this tell? Being a Chinese and having quite a bit knowledge at the consumer electronics production in China, I would tell you the following:
1. The MP3/MP4 players markets in Chinese in extremely cut-throating. There are over 20 brands and all of them uses pretty much the same 2-3 chipsets. The manufacturers are forced to release immature products to the markets, to gain market share with gimmicks/new features before loosing it to the other brands.
2. Teclast is such an company in the above mentioned category and the initial batches of the T51/S:flo2 are immature product, not only in terms of firmware, but also in terms of key components selections (e.g. screen, battery, volume control, capacitor/resistor with accurate values). The people in the Chinese forums have many discussions on the differences/issues of 09 week 43, 09 week 50, 10 week 20 batches of the T51
So my advices are:
1. Never buy the initial batch/releases of ANY Chineses brand MP3/4 player (the same applies for some Korean brand players as many of them are also made in China).
2. Wait till at least the 3rd or 4th firmware updates, to find out if the problems are caused by buggy firmwares, or fundamental designs issues.
3. Be prepared that some issues will NEVER get fixed, no matter how it seems to be an easy problem to fix.
4. Never hot unplugging the USB cable in data connection mode. Otherwise sooner or later you will corrupt the file system or worse, toast the flash memory.
I waited till firmware V2.0 and 10 week 20 batch of the T51 was announced before I made my order of my S:flo2. But I still have to accept the fact that the issue of not displaying OGG file ID3 will probably never get fixed.