I wouldn't use them in a high security location or in a corporate setting in general, but I personally feel fine using them in a home setting. The software on the managed Hasivo switch I have is clearly basically a slightly modified version of the Realtek SDK code base, which is also why it has so much in common with other switches from more well-known brands using similar generation Realtek switch chips.
Do I know for sure that there isn't something extra running on there? No, but at least I didn't see anything immediately weird when tearing apart the firmware image.
Don't get me wrong though, the web interface on mine has a security issue (exploitable with LAN access) as far as I know, and a number of bugs. Some other models are better in that regard.
Hopefully we'll eventually see OpenWrt support for some of these (already WIP for some) to iron out bugs and provide future updates.
