I've thought about it, and I keep waffling back and forth over which FRPG I really want to run.
As a player, 4E isn't my favorite iteration of the game ever. As a GM, it's the easiest to prep for since AD&D 2nd edition.
As a player, Pathfinder allows me a ton of options using a system I like almost as much as I liked AD&D 2nd edition. As a GM, having all those options makes game prep more difficult because not only do I have to design NPCs around that, I have to keep in mind what the PCs are capable of and I'm really bad at remembering that. Plus, there are no electronic tools I'm aware of for encounter design (at least, none that are as easy to use and as fast as the 4E Encounter Designer, or even the 2nd ed. Core Rules CD-ROM).
So, I'm torn. There are other good systems, to be sure. AD&D 2nd edition was a lot of fun in its day. Hackmaster looks really good now, too. Finding players can be problematic, unfortunately. Around here, a lot of people play D&D. Not only that, they stick with whatever the current version is. I know a couple of people who have bought into Pathfinder, and maybe one who would still have his 2nd edition stuff, should I choose that route.
I fear I will be limited by what my players will be willing to play. I'm OK with it if I can only find 4E players. Maybe, over time, my feelings about the game will change; I've only recent rediscovered my love for 2nd edition, after all. Frankly, as much as I like Pathfinder, I'm reluctant to run it because high-level play is still wonky (not that I've ever had a campaign last that long) and game prep is a pain. It would probably be OK if I could just stick to running Adventure Paths. 4E, on the other hand, has electronic tools that can speed up my game prep to the point that I can prepare a whole session's worth of adventure in just a few hours.
If it turns out that I join my next game as a player, instead of a GM, then I think my position will flip: I'd rather play Pathfinder than 4E. I'd rather GM 4E than Pathfinder. I actually find Hackmaster to be too complex and fiddly, but if the only game I could find to play in was Hackmaster, I would gladly play. If someone was running a different FRPG, well, I'd have to evaluate that on a case by case basis (unless it was D&D BECMI, or AD&D; I'd play those again for sure), because I only own three FRPGs (D&D in various editions, Pathfinder, and Hackmaster Basic).
To me, they fill different niches; they scratch different itches. I'm fortunate in that I have sufficient disposable income that I can have a library full of different RPGs, and if I don't have one, I can acquire it with a minimum of effort. Sadly, that also means I sometimes have to actually decide which to dedicate myself to for a significant length of time while I'm surrounded by people who aren't willing to pick up a new game for just a few sessions of change.
If you find a good group who plays Pathfinder, a group you get along with and have fun with, I see no reason not to switch. On the other hand, if you find the same thing in a group playing 4E, play with them. If you can find both, and have time for both, then ... live the dream, my friend!