I've reviewed at least four PlayFi devices here and possibly more and each time, I've devoted longer to talking about the OS than any rival with the exception of Roon that got a complete review of its own.
As of now (September 2020), using PlayFi in the critical listening mode is sufficiently close to gapless that it will do for most listeners. Now, you'll need to pay attention to 'most,' it's an important, structural word here. If you listen exclusively to segued material, it might not be sufficient but in any other case, it probably is.
In use, PlayFi is now, in many respects less of an irritant to use than BluOS which remains tied to an annoying queue system that- personally- I find much more of a bugbear than any gap. Of course, BluOS is gapless so if that's more important to you pays your money and takes your choice. Naim's OS is better than either but ties you exclusively into their product range for which you'll need to budget accordingly. Neither of those OS can get within a mile of the whole house options that PlayFi offers thanks to cross company support. It's almost... like in the context of these reviews, I'm invited to consider the wider context of the product beyond a single feature and make findings based on that. If you are embarking on the migration from a CD collection to a streaming one, the Quad has functionality that is going to matter to would be owners a great deal more than what happens between tracks. It would cost another £1,900 to choose a Uniti Star (which can also play CD) for example.
Ultimately, if you want the best O/S out there, you should pay for Roon and choose decoding to suit. It's not even a close run thing either. However, since I can't have a Francis Fukuyama moment and declare the end of streaming as a result, we're going to keep looking at other devices. Scoring will always be based on a full matrix of performance, build and functionality and I'm entirely sure that at times, people are going to vigorously disagree with it.