I've got my iPad for only 2 months now. Financially, No. It is hard to value the device on itself; as said before in this thread, there are quite a few aspects related to this.
For one, actual financial savings: thanks to the 3G feature, it saved me A LOT of lenghty phone calls for looking up some information. Driving to a client/contact and remembering all kinds of stuff I had to look up (I know, bad preparation), I used to call home for it. Now, I just grab my iPad and look it up. As I use prepaid cards for phoning, these calls used to add up quickly.
I also never got a GPS, even though I planned for it. Now, I don't need it anymore (even though maps is kind of slow on Edge still, but don't need it that much

). And yes, I have no smartphone which has the same feature

.
On the other side, you have time saving due to efficiency. Time is valuable. I used to print a lot of stuff, because my laptop is a slow booter. Now, I just open up iPad & Goodreader or Notes, and I've got everything I need. After a meeting, I can instantly mail my notes to all attendees. Got a phone call? Check calendar on iPad, and immediatly plan a meeting right there (yup, still no smartphone, but I absolutely love iPad's screen size, it's just perfect for these kinds of things, in my opinion).
As I recently graduated, it is also useful for showing off my CV when at a sollicitation, and immediatly leaves those people with an impression of someone who is well-organised, flexible and efficient (again, refer to calendar). That same impression is great for contact with clients or business contacts too.
As said, it hasn't paid itself back (yet?), however I believe is worth it's money twice in my humble opinion, if I think to all my other uses for it ("media center" for watching videos/movies, reading iBooks, listening music, sometimes gaming...).
I must admit, that my apps I thought would pay back quickest (pages & numbers), are actually nearly unused on my iPad. If I have a computer to my disposition, I rather prefer editing on there. I do believe it is very useful to for example salesmen.