Let's see...topics covered:
Pathfinder: Overall, I like it more than I dislike it. I love the way they made all classes worth staying in instead of PrCing out ASAP, even if certain ones didn't need the help, like the monster-as-PC rules (even if they are a bit on the OP side in many cases), and think the consolidated skill system is fantastic...but I don't feel they went far enough in improving certain classes or weakening others, I hate how special maneuvers were gutted (CMB/CMD would be a good concept, but they botched the math on execution), and feel a lot of their fixes to spellcasting were hit-or-miss.
When I play D&D, though, I'm happy in either 3.5 or 3.PF, though the occasional person (more RL than online) who considers PF to be a sort of holy grail of balance and perfection compared to 3.X's cesspool of brokenness grates hard. The systems are still similar enough that you can judge if something would be overpowered when ported into PF by if it was OP in 3.5 to begin with. When I DM, it's a horrific hackjob composed of every bit I like from 3.5 and PF, plus my own personal foibles regarding the bits I don't.
Psionics: If I could, I'd marry the psionics rules, then homebrew a Half-Ruleset template so I could give it babies. I've loved them since they came out, and consider them how magic should have been written in the first place...Vancian casting is an awkward white elephant, one I accept but have no real attachment to. Complaints about how psionics belong in sci-fi settings have always bugged me too, but I attribute that to the fact that some of my earliest fantasy literature was Mercedes Lackey's Valedemar books where
psionicsmental magic is the default and 'arcanist' magic is the optional ruleset. The 'tattoos, ectoplasm, and crystals' default flavor is irritating, but I'm also a vocal proponent of refluffing everything and anything I get my hands on.
Other games: I've always wanted to play Shadowrun, but among non-D20 games I've played, I really like the Dark heresy/Rogue Trader/Deathwatch mechanics engine. The printed material is pretty heavily tied to the setting (which is awesome), but the spend-XP-as-you-earn-it-to-gain-"levels" is far superior to d20's class-level system, while better IMO than completely granular XP-based systems like GURPS or WoD (either flavor).