Old School Feats got a new review over Pseudonym Writes. You can read the whole thing here. Here is the conclusion:
SHOULD YOU BUY THIS BOOK?
Overall, I think it was a very fair review, even the criticisms.
OSR feats does not fit perfectly to non-B/X systems - I don't think it would be possible to create a book of feats that worked for both Knave and The Black Hack, for example, so I chose to stick with a single system (which happens to be my favorite, and also the most popular right now IMO - since it is very close to OSE, LL and BFRPG). But, as he says, the ideas are adaptable for other systems.
I also agree that it is not perfectly balanced. I do think, however, it IMPROVES balance when compared to baseline B/X (which is an issue the review addresses in the last sentence).
Finally, the book was indeed written with a great effort to be perfectly compatible with B/X, using existing classes, skills, mechanics, etc. I avoided adding new mechanics or more complexity. I DO think it is possible to improve some aspects of B/X, however, and I've already written a system with this in mind (Dark Fantasy Basic).
TBH, I'm a bit torn on these two approaches: keep things perfectly compatible with B/X, to reach a wider audience, or do my own thing, changing every bit of old school D&D to better suit my needs and to make a complete, coherent game of my own, mixing B/X, OSR, and modern stuff.
Let's see. For now, I'm tackling races. In 2023, I might do something more ambitious: either an entire book of B/X options or a coherent Dark Fantasy Compendium. Let me know if you have a preference for either one!