I have owned many raspberry Pi's over the last decade. For the most part I have been pretty satisfied with them as development and project platforms. The Raspberry Pi is well thought out, well designed for its purpose and is well supported by both the manufacturer and the community that has grown around it. What I have not been satisfied with is the third party hardware market that has popped up.
Let me say upfront that not all the hardware I have ordered over the years has been terrible, some of it has worked perfectly. However, the vast majority of these things have failed in some major way making the product either barely usable or not usable at all. Case in point, I recently bought a HyperPixel 4" screen from a company called Pimoroni. This product came highly recommended and was well reviewed and the instructions for getting it working were on the surface fairly easy.
My problems with this device started very early, at first, it would flash on for just a second and then the screen would go blank for no apparent reason, the Raspberry Pi was working fine, I could plug it into the HDMI and get video fine, I could plug other devices into the GPIO and get it working perfectly fine. After 2 days of troubleshooting this, I figured out that the I2C drivers interfered with the screen working properly, when ever those drivers polled the GPIO pins the screen would blank and not come back until a hard shutdown occurred. Completely disabling I2C and SPI on the system made it slightly better, as I could then use it for several hours before the screen blanked. There was absolutely no mention of this problem in any of the documentation anywhere, nor was there any mention of the problem on the Pimoroni forums. I thought maybe I simply had a bad screen, maybe it was just sensitive to the voltage being put out by the GPIO, so I put in an RMA request and pretty quickly, I received a replacement, same exact problem. At this point, I just gave up on it.
Again, if this had been the first time I received a half ass product, I probably would not think much about it, but over and over it has happened. It is a really sad state of affairs when I can jury rig something up on a breadboard from spare parts that works better than the professionally built version. Unfortunately I do do not have any good advise on how to tell the good from the bad here, these crap devices are often well reviewed and have very few publicized problems. All I can really say is, if you can build it yourself, do it, if you can't, well, "May the buyer beware!".
As a side note, if you are looking for a 4" screen for a Raspberry Pi, Miuzei makes a pretty good Touchscreen that works as promised with very few issues, my only real issue with it, is it does use the HDMI port, but that is not a show stopper, it just adds a cable I was looking to avoid.