There are numerous things you might want to consider like:
1.) What you plan on doing and how comfortable you might be without a keyboard. If you're emails are short and to the point, you might be able to get away without one.
Yes, you CAN buy a keyboard attachment for the iPad, but it's gonna cost you extra money. That will not only raise the base price $70, it's another thing you have to carry around with you. The Netbook's keyboard is already attached and it's included in the price - which brings us to...
2.) Most netbooks are a bit cheaper than the iPad to begin with. The Dell Mini 10v can be had for as little as $249. Lenovo's offerings start at $359. HP's netbooks start at $269. That's in comparison to the iPad which starts at $499 for the basic model.
3.) The Apple universe is a walled garden with lots of limitations. Since the iPad runs the same operating system as the iPhone/iPod Touch, this can be an issue. You'd have to buy new apps to do some things that don't come with the device. Yes, there are free iP___ apps out there as well.
Netbooks, on the other hand, will run any and all standard PC software given they're based on full versions of Windows (or Linux). If you're really a die-hard Mac fan, there are even tutorials on how to set up certain Dell Mini 10's with OSX. If youv'e got a licence for the software and it's OK to install it on more than one device, you can install it and use it on either one. It may be cheaper to go this route.
4.) Then there's the issue of what sort of stuff you can or can't do with the iPad. It's primary purpose is as a fancy ebook reader. But as such, there's been a recent controversy with regards to how Apple is going to require ALL content to be approved (read: censored) before it's allowed onto your device. Amazon and Barnes & Noble have both released or announced ebook reader apps for the iPhone/Pod/Pad that have been approved. The issue is the content that will be banned from your iPad. If, for instance, you have a subscription to say, Playboy or Maxim - you will NOT be able to read either magazine on your iPad.
You can, of course, read them from the comfort of your home PC by way of the desktop version of the ebook reader - but it won't sync to your mobile device.
While it might be considered "OK" and "PC" to keep the iP_____ family of devices porn and smut free, it begs the question - "What's next on Apple's list to be banned?" Given Apple's track record, that's hard to say. They recently purged something like 5,000 apps from the iPhone store because they were deemed "too racy".
Who knows - Steve Jobs may get an itch and decide that only certain politically oriented content that agrees with his personal views may be allowed and all else is banned.
Or medical text with graphic depiction of various body parts could be banned simply because they're too suggestive.
Either way - it's not an issue with the netbook. You can have pretty much ANY and all content on them regardless of how they're rated - G, PG, PG-13, R or XXX for that matter.
5.) As far as battery life goes - That's hard to say. It will depend largely on a couple of things - like how you use the device. Since we haven't got a working iPad to put through the proverbial testing mill, it's hard to say how well it will live up to what Apple claims the battery life will be. Either way you go, you'll likely need to keep charging the devices. All of these devices come with the usual charging cables and stuff you need to keep them going.
Netbooks, as a general rule have user replacable batteries. That is, if your battery is running low, and you're not quite done with what you're working on, you can shut the device down after saving your work, pop in a fresh battery and go on with your life. The iPad - not so much. It, like the iPhone and iPod Touch comes with a battery that's sealed inside of the device. You can't replace it yourself. You'll need to take it back to an Apple store and they'll replace the iPad - lock, stock and barrel for $99. It would be also a very good idea to sync your device with your primary desktop before turning in your iPad for replacement as anything on the device will NOT be extracted...
6.) Netbooks, typically come with 160 GB or larger drives which are 10 times larger than the base iPad hard drive (only 16 GB). If you have a large music collection you want to bring along with you, or if you want to bring movies along for your trips, 16 GB may not be quite enough room. The largest drive space available to the iPad is 64 GB - half as much as the ones typically found in base line netbooks.
7.) About the only thing that the iPad excels in would be in the realm of "cool factor". If that's an important feature, more important than productivity, then by all means, there's your answer.
The bottom line, if it were my decision, I'd go with the netbook. They offer more bang for the buck. But hey, I'm less concerned with looking good as I am with getting the job done.