DISCLAIMER: As a GM, I haven't used Pathfinder for any of my campaigns in quite a while, and the following is 100% based on zero quantifiable facts, simply the opinion of me and my group. Our group has all played D&D since the old days, through AD&D, 2E, 3E, 3.5 as well as many other gaming systems - fantasy and otherwise. Many in my group also GM. I remember - back in the day - when Pathfinder first came out, we took a look at it and said things like... "Ohh, that's nice" "That's a great improvement" ...and similar platitudes. I can't remember us having much bad to say about it at that time, and over the years we never felt the need or desire to go back to 3.5. We looked at 4E when it came out, of course, but there wasn't any desire from any of us to switch - we simply didn't see anything worthwhile. The amount of material and support for Pathfinder is now staggering, and I don't see any signs of it slowing. Paizo has a rich campaign world with Golarian, and is still producing quality content in the form of their APs, not to mention 3rd party content is also vast. I personally feel that power creep has taken over the system, but for many people that's a good thing. Just be sure, as a GM, that you review all material beyond the Core books to see if you want to allow it in your campaign. Be certain your players know that just because something is printed with the Pathfinder logo on it doesn't mean you will automatically allow it in the campaign, as some choices can be very unbalancing depending on your campaign.