The 60% form factor is great, but there are two problems. If you try to squeeze in arrow keys, the layout becomes non-standard, interfering with typing and making it difficult to find replacement keycaps. If you do not have dedicated arrow keys, you can preserve the standard layout for ordinary typing and easy keycap replacement, but you lose ease of navigation.
Recently, I went from a full-size to a TKL. This transition was fine. I then got interested in smaller boards and tried the Poker II, Tex Beetle, Leopold FC660M, and Keycool 84.
The Poker II has a standard layout, but no dedicated arrow keys. My productivity suffered because I use arrow keys a lot. The Tex Beetle has great build quality and an elegant appearance as well as dedicated arrow keys, but the small right-shift and non-standard z-row staggering adversely affected my typing. The Keycool 84 has dedicated arrow keys as well as F-keys, but I was not pleased with the build quality or appearance. The KC 84 looks like a jumble of keys jammed together, and the non-standard size or profile of some keys makes keycap replacement difficult.
I had the best luck with the Leopold FC660M. I did not miss the lack of dedicated F-keys, and I appreciated the dedicated arrow keys. The layout is almost standard except for a slightly shortened right-shift. However, the fact that the right-shift is non-standard and that the spacing of the mounting stems in the spacebar are non-standard makes keycap replacement a bit of a challenge.
Overall, although I like the idea of going sub-TKL, I have not found any such board to be completely satisfactory. Consequently, I have gone back to using my IBM SSK as my daily driver. It has everything I would want in a keyboard: TKL, detachable cable, dye-sub PBT keycaps, embedded numpad, excellent typing feel, agreeable sound (at least to me), and superb build quality and fit and finish.