We've been playing Pathfinder now for some time and I have to give a bit of credit to the system. First of all, it's available free of charge, at least at the moment. Who knows what the future brings but at the moment, the core book is completely free. Other Pathfinder products are, compared to WotC books, reasonably priced, so if/when the final Pathfinder RPG is getting a price tag, it is most likely being the cheapest D&D core setting ever anyway.
Usability of Pathfinder Beta book is very good. Like said above, it includes DMG so no need to worry about carrying that tome to the playing table just for a few odd rule checks.
On the rules change over vanilla 3.5, I have to say in our group we all like it. We are playing without any house rules and that already should be saying something about the quality of the revision.
On Pathfinder in general, I don't like their artwork and I didn't like the first adventure path, also the few other Golarion-based books I've red, to me they were not anything special. But the core rules are strong. To anyone I'd say go for it, unless you prefer True20 which is also very solid.
So is it worth it? I paid 15 dollars from my hard copy of Pathfinder Beta and 90 euros from D&D 4th edition rulebooks. After a few weeks of play 4th edition lies forgotten in my bookshelf while Pathfinder gets taken out every week.