I'd love to know what you actually do with yours. Every single use case I could come up with for the iPad was totally destroyed by the iPhone 4, which has 80% the resolution but fits in my pocket. If a new iPad came out with a reasonable screen I could totally see it being an awesome device, but at 1024x768 people really just need to learn to hold their iPhone 4 closer to their face.
Email, Web browsing, reading technical books, games, photo storage, photo editing, slideshows, watching TV, Twitter, Facebook (even though theres no native iPad app annoyingly), reading (particular technical books where the extra screen real estate really shines), reading my RSS feeds, etc.
I have n iPhone 4 too and will certainly pull that out of my pocket and use it but at home I just prefer the larger screen.
Composing presentations, preparing invoices, sketching, Monkey Island, writing.
The retina display makes a huge difference for reading, so I tend to use the iPhone for feeds and things, but for anything creative the iPad is the clear winner.
The bigger screen also makes it a great trip/car browsing device. It's sinmply not comfortable to do extensive browsing on a phone. The iPad's niche is the middle-ground between a phone and latptop (between walking mobile and mobile office)
