Good point, but why label those as "attempts"? A decade ago PDAs were pretty good devices with decent amount of free apps and an interesting range of possibilities. (For one, they were extensible via cards. Something that's not available in today smartphones I know of.) You could read books, play games, use internet via WiFi, plus there was a lot of business applications for them. Heck, my old Asus MyPal has better book reader and calendar apps than I have on my current smartphone.
Sure, there wasn't a marketing hysteria around PDAs, but they were a viable market of their own.
I loved my Toshiba M200 (http://reviews.cnet.com/Toshiba_Portege_M200_tablet_PC/4505-...) way back in 2004! I used to use it during my graduate classes to take handwritten notes. It's a little sluggish by today's standards, but lighter weight distributions of Linux still run pretty well.
Asus MyPal (a relatively high-end PDA) was around $400 when I bought it. That is cheaper than modern high-end phones and roughly equal to the prices of mid-level phones.
The laptop I'm writing this from costs around $400 dollars as well. This is the price of the cheapest iPad.
If the Palm Computing IPO didn't reflect marketing hysteria around PDA's, I don't know what does. The spinoff gave Palm a market cap of over $20B, about six times the entire value of its parent company, 3Com.
http://en.wikipedia.org/wiki/Windows_for_Pen_Computing
http://en.wikipedia.org/wiki/XP_Tablet_PC_Edition#Tablet_PC_...
http://en.wikipedia.org/wiki/Pocket_PC