There isn't a way for me to test drive an Arduino without buying one.
Unfortunately not.
A few people have been trying to do a virtual arduino thing with code interpretation but I don't think it has got very far.
I would have thought that the vast supply of arduino code, libraries and the massive forum might sway you this way.
Trying not to be biased: It is better than PIC chips (yes it does not have USB circuitry in it - you need a serial to USB chip which is on board the arduino duemilanove and many other boards). It is however much larger in terms of code examples, libraries and forum support.
ARM based boards are more powerful but also have less support etc. and most people do not need that much power (you can do most things with an arduino (ATmega chip)).
It obviously depends on what you are wanting to do as to whether it suits you. Use the search and take a look for the kind of thing you might want to do to get an idea.
I think that's the best I can do!
Mowcius