I have Obdstar x300 dp full (Yellow model) and it is working well, only with newer models needs to connect to the internet, example: odometer correction to 2015- Ford F150, I just renew the yearly subscription (us$200) and keeps updating almost daily.
I don’t know if the x300 Dp Plus is substantially better than the first model, the difference in price is high.
The new x300 dp plus comes with new functions like “ecu programming” and “ecu clone” (I can’t find information on what models can make with those functions), now have a new RFID adapter (P001) and they discontinued the support for the old RFID adapter, no updates.
For diagnostics it’s very limited, almost no special functions,.
For key programming and pin code retrieval is good, not all brands and models but can make many models without issues.
For odometer calibration is good, better than EZ500 (I have this tool too).
In my own experience, the money invested was worth it.
The obdstar x100pro was just an example of discontinued support, same can be said for x300m probably.
I agree it’s cheap enough to buy and you will more than make your money back, i did on my x100pro and I only used it a couple of times