I think the only kink issue with the Pi 4 is that the power design is not compliant. The two CC pins are sharing a single resistor instead of having their own resistor. This causes problems if you use certain cables or chargers. But with the standard official power supply there is no issue.
The best rule to follow with Pis is
always to use the appropriate standard official power supply. The Pi forums are full of people who discovered this the hard way. Pis require a constant 5V supply that does not 'sag' significantly under load. Many 'bricks' sold primarily as chargers cannot sustain their rated voltage up to their rated power output.
Every other issue discovered with the Pi 4 is or will be resolved firmware updates. Overheating...solved via update.
Not really! Recent firmware updates have improved the heat generation at low to intermediate loads somewhat, but, AFAIK, a Pi 4 will still overheat and throttle under low to moderate loads in a closed case, while the firmware mods have not affected the heat generation under maximum load - where fan cooling or other substantial cooling measures are needed to avoid overheating and consequent throttling.
What else is there? Buster problems?...wait for updates.
Most people have not been affected by these, and they are relevant to all Pi models.