I still love my iPad.
But the lack of multi-tasking and iOS4 in general is really taking it down for me big time.
Since I've gotten my iPhone 4 I've used my iPad less and less. It all boils down to the lack of multi-tasking.
I've gone back to using my MacBook and PC laptops more in the last month than I had used them in the entire first few months of owning my iPad.
If I didn't own an iPhone I might have gotten an iPad 3G. But my iPhone 4 does everything the iPad does portable, except a few things that I would never realistically use away from home, like Pages. My iPhone 4, in fact, does more. Thanks to the camera.
The iPad also has a problem with app support. Far too many developers have the attitude that if their iPhone app works for the iPad then thats good enough. Then you have other developers that try to charge you 2-3x as much for the iPad version running at 1024x768 when the iPhone 4 version, costing significantly less, runs at 960x640. Why should I pay $10 for a $3 app just for an extra few pixels? I bet in a week here we'll see Madden released separately for the iPhone and iPad, one costing $9.99 and the other $14.99 and they'll be the exact same game, just different resolutions.
So, in short, the lack of iOS4/multi-tasking, and the way app developers either ignore iPad or try to milk it for far more than its worth is killing it for me. I'm sure that once the honeymoon period starts wearing off for people they'll think the same way.