I run 3.5, with a variety of rules from Uneathed Arcana, Pathfinder, and Trailblazer.

From TB, I use:
*Iterative attacks
*Combat Reactions
*Vision rules
*Other odds and ends from classes.

Most of the rest of what TB addressed I had already addressed. I wrote a standardized magic system with UA spell points that fixes the system much better for me. The action point rules for TB I didn't understand and they didn't seem to do what my existing action point rules did. Combat maneuvers had already been handled by Pathfinder so I saw no need to revisit that. The big concept I took from classes was the idea of a circumstantial attack bonus covering the difference in BAB between 3/4 and full, but I had to rewrite the rogue myself to get my vp/wp system and for various other reason.

TB also dumbed down a lot of things that I didn't feel the need to. I'm fine with skill points, and although I understand the rationale behind consolidation I see no impetus for me to do it since my players understand the existing system. And I like putting one rank in Perform (Sing) every now and then. I also didn't like the standarization of saves; I actually added in a medium save to differentiate the classes more based on saves, not less. I've never had any real issue with overpowered spells so I didn't look there. I kind of liked the standardized weapon rules, but saw no need to explicitly implement them. Per rest mechanics is another example of something that is fine but I just didn't see the need for.

The broad conclusion is that after having played the same game for over ten years I know what I need out of it, and I pick rules that get me there from any number of sources.