Looking at it, honestly, it's something I'd use instead of a laptop for a lot of cases, from sitting around in a coffeeshop to catch up on feeds to going to conferences (since it can do Keynote, which is the only thing I currently actually need a laptop for).

The highlighting stuff in Keynote (telestrator mode!) looks seriously awesome.

Imagine you're in a VC meeting and you're doing financial projections. You could all stare at a big screen, or you could put one of these down in the middle of the table, say "here, let's work on it together!" and you're away.

It's all about the form-factor and the utter reliability. This is a great replacement for a road-warrior meeting laptop - what the MacBook Air was trying to be - and it's the ideal computer to buy for your granny or your kid brother who wants to check their email and write the odd letter.

(Much less use if what you do on the move is program, but that's OK. It's not aimed at you.)

Pretty much. I almost never do actual coding at a conference; I do my talks, I take notes in other sessions, I read interesting links and occasionally pop in to IRC. I don't need a laptop for that, but since the laptop's the only thing I have which does all those things I end up taking it.

Plus the iPad would probably be a nicer device to have with me on the plane...

Personally I think it's a complimentary device. Some apps are just going to work better with a multi-touch interface than a traditional keyboard/mouse setup. Judging by the amount of new UI elements it appears you can write some serious, near desktop quality, applications for the iPad. I think a very common usage scenario is going to be using the iPad in conjunction with your laptop or desktop. For example, I think multi-touch web browsing is a much better experience than a keyboard/mouse browser experience. It's just easier to move around pages and zoom in. If I had an iPad sitting on my desk next to my keyboard and mouse I suspect a good chunk of my browsing would be done on the iPad.