The problems with Greetech are:
- The best-sounding variant (black tops) is probably not even made anymore, and tends to only be available on Taobao
- They can be really inconsistent, some are scratchier than others, and the stock springs can be all over the place in weight
- They tend to only be available in plate-mount variants
- Generally don't work with switch films
This makes them pretty much unsuitable for "high end" custom building. But for just dropping something into a hotswap board, yeah, I can vouch for them. They take well to lube, although the sound always tends to be a bit high-pitched. For the money, though, you're usually better off buying Gateron nowadays. In the past, I'd say Gateron and Greetech were comparable quality, but as of 2021 Gateron generally makes a better switch for typically around the same price.