I have Maxwell in my 3.5 f, it is great, but it does also have split image, which for me is far more useful the microprism. But, ether one is not a fix for every occasion. At the same time, even if split image gets blacked out, or partially so, it is still often there just need to change the angle from which you're looking at it. Microprism in my experience, once it goes, it just goes and on some background patterns it is no help at all, in fact makes things more confusing. I think there is a reason just about all camera makers have come up with variety of screens, depending on need and application. Micro/split combination is still probably the most universal one when faster focusing is needed. For times and places where there is time and photographed detail needs to be examined during focusing (so focus goes where intended), plain matte screens with center spot have their place.
Also let me add, that looking through many older SLR's with microprisms in, there is a significant difference in viewing experience Some have coarser micro-pattern than others, and that makes a difference where and when one will become less useful.
To put this in perspective, I do not like Pentax 645 NII because of how hard it is to focus manually with standard screen, a far far cry from original P645 with its micro/split combination standard screen when things just pop nicely and convincingly.
When I shop for (yet) another camera, I tend to value it higher if it comes with micro/split screen. As for Oleson screens I have no experience and I hope he gets his stock from a reputable maker and continues to do so. There are a lot of screens from China that make all kinds of claims, often they prove to be a total waste of money. Given Oleson's reputation thus far, he seems to be a good bet at prices that may still be competitive given the results. I can vouch for Maxwell, but I paid a $100 for mine, I believe that is a long gone price.