The PhysX/Newton/... implementation won't change the way you work with the physics engine in GS. PhysX is very robust, has a nice interface, tons of documentation, is fast (probably faster than the others) and it does provide a particle solver too. PhysX provides even more features then Newton, these are no arguments against PhysX.

A nice feature PhysX also provides is an remote debuger. With this, you can watch your world as physical shapes in an standalone application, interactively change params like the mass or add forces with your mouse _while running the game_. This helps you to fine tune your physical values and to find seldom bugs.

The only downside of PhysX is the current driver size, at this point I absolutely agree with you. But as I said, more and more games will need the driver. It would be interesting to see some statistics how many people have it installed.