My 64GB WiFi iPad has served me nicely for over a year and I'm anxiously awaiting the iPad 3 to finally get a camera, more speed, 3G, and SD card and USB support (a girl can hope) in a slimmer package.
Upon the announcement of the HP Touchpad, I salivated for a second because I respect WebOS (hate HP) but then decided against it (no 3G yet, few apps, and a bit bulky).
Then I thought about what incentive it would take to make me leave the iOS platform for WebOS or even Android devices. I think would be the same thing that motivated me to get a Palm Pre Plus -- free (or less costly) Hotspot. It is the ONLY device that does that. If HP decides to subsidize a carrier and provide its tablet with no/low cost 3G, I might give it a try.
I doubt that will ever happen so I think iOS will remain in my tablet using future. :p