In terms of saving money, no I could have used another device (laptop or iPhone) to accomplish the same. Typically my iPhone (or any smartphone) has saved me money as it goes out for the day while the iPad may be in the safe.
For leisure I won't bring the laptop as I'd rarely need more than the iPad so it's a big space/weight saver. It works best for media consumption, web browsing, email (I have a folding bluetooth keyboard), and photo backup (copy to iPad, copy to cloud). Photo organization leaves a bit to be desired (I'd like to be able to update my iPhoto library on the go which isn't possible currently). The flash limitation isn't that big for me.
For business trips it's a wash a best as I still carry the laptop but just skip the extra battery and media drive. I don't have access to the corporate VPN on the iPad (fortunately I DO have access to email/calendar w/o VPN access). If I did I think document limitations would be an issue (shared drives, MS Office track changes, PDF creation, etc). Also I work off a X11 term a lot (need full X11 access and a ssh term won't cut it).