I think the main thing positive is that the RedFly has no hard drive, no RAM, no other 'hardware', so the price you pay is the price you pay. No software costs. No setup costs. No maintenance costs. Virtually nothing to break if you drop it. No files lost if it gets stolen.
If you are not a business user, most of the above may seem kind of irrelevant, but the total cost of owning a (say) $500 laptop is more like $2,000 or $3,000 for a typical business, by the time you include software, support and maintenance costs throughout the lifetime of the device.
Also, you can **always** have access to everything, even when you don't carry the REDFLY, since you can easily carry your phone anywhere (just about).
Battery life - the REDFLY will easily last a solid 8 or 9 hours. Not sure netbooks can manage that.
Negatives?
You are limited to just what your phone can do, unless you can remote-access a desktop or laptop.
No video support on the REDFLY screen.
No peripheral support - DVD drive, printer, speakers, microphone, wireless etc etc unless it is provided or supported by your phone.
No way to upgrade the REDFLY - so no RAM or HDD upgrades, but then on the plus side, you can always upgrade your phone.
Limited video support also means limited game support, should you care.
Not so cool as a netbook, from a *consumer* perspective.
I'm sure there's more + and - on both sides, but that should help you start to weigh up the two sides.
Oh - check out this video demo
http://hooktours.com/8072474/