Internal beta testing generally only catches bugs that cause issues when the device is used in the way that the engineers expect it to perform. Outside beta testing catches bugs that cause issues when the device is used in the way that engineers didn't expect. Even large companies still often use outside beta testing, as no amount of internal QC can really catch every consumer interaction with a device. It's very easy to criticize after the fact, but from engineering perspective it's hard to define tests covering every conceivable consumer interaction while also justifying that it isn't redundant of others.
As to the battery cover, I find it very easy to remove and install. The only thing I do is clean the grooves with a Q-tip on occasion to remove dust and grime buildup.
Finally, as to your last comment, I'd say having upgradeable firmware is big step-up versus other competitors, so maybe those competitors need to step up too in that regard if they want to play in the world economy and so on. After all, despite any complaints, YiHi can fix things with a firmware update. That certainly hasn't been the case with all of their competitors.
I agree with your last statement (here's a hint Evolv and Provape USER upgradeable firmware).
However, their has been NO official response from Yihi about the battery / Eco mode fix. Nothing, nada, and the firmware should have been pulled. As has already been addressed, how many have this device that arent poking around on the forums?
You cant out of one side of the mouth complain that your users shouldnt be charging via the USB port (short of saying the USB port isnt mounted correctly), instead, telling your users to swap batteries using the battery cover, then implement a mode called Eco that when said battery is removed instead of using the USB port as was originally intended to swap the battery, essentially soft bricks the device.
Its not acceptable and its unbelievable, in fact, frustrating that we dont hold these companies accountable, instead, giving them a pass every time they do something stupid.
The software in the SX Mini is simple. Its not complex at all, if I had the source code, Im sure I could completely rewrite the menu system in a day or two and make it much more user friendly with a few basic features that should be included in the device that currently are not (screen timeout and temperature saving in the presets for starters, this of course depends on how much user storage there is in the device as to whether this would be possible, but if there is enough space, there is no reason user temps cant be stored).
In fact, if Yihi open sourced the code, the user functionality of this device would explode, users could add features, change the menu and designs, etc. But every company is afraid to allow their community and fans to do this. It requires the bootloader to be non-writable so that users could easily restore to factory firmware if their device bricks (a non-writeable bootloader makes the device unbrickable) but my guess is that they dont have a non-writeable bootloader, ie. the bootloader is included in the firmware, which is creepy - you can tell because in order to turn the link on, the device has to be booted, theres no emergency recovery process.
To make my point above, take a look at routers, there is a reason companies have decided to let the community design the firmware for their routers rather than taking the responsibility for themselves. Asus is one such example, they have several routers where the included firmware is Tomato or DD-WRT (open source, community written firmware) and Asus is only responsible for the hardware.