I've only ever been happy with one brand (and they are an Australian company so does you no good). But I mostly roll my own. What are you looking for as far as people/days?
Certainly, once you have a main bleeder kit, that's going to cover a lot, but I've packed some pretty extensive "boo-boo" kits based on duration and group size.
I usually take stuff for blisters and small cuts, wound cleaning and holding (steri-stips are great) Non-adherent dressings and the type of wide bandage tape that has a paper backing. There is also a film dressing that works really well, but you need to know what you are doing a bit. I really don't carry a lot for small wounds, my main concern is making sure I or my patient survives to evac, which here is basically a snakebite bandage (and really I know a lot of guys who carry that and a bandanna as their FAK)
As much as people talk about improvised splints, a SAM is very handy if you are the one injured. Improvising is cool, but when that means you are using up your actual gear for the wrong purpose, I wonder if it's always the best call.
A huge factor is the bag, and how it's stored. My current main first aid kits waste a lot of space in organizing pockets, but they are fine for the house, and car. My walking kit is basically a zippered clamshell with two pockets. Some people fall in between. One good method is basically a tool roll that then goes into a dry-bag. Easy if you do any sewing.
I'm sure some other guys will throw in brands and vendors, but that's a starting point anyway.