The answer is simple, if you are tight on money buy the iPad 1 if not splurge on the iPad 2 given availability of course.
Penny wise, pound foolish. It depends on how long you hope to use the device. The dual core processor and 512mb RAM update will most likely support not just iOS 5, but probably the next few updates as well. It might be worth the extra cash to buy the current model.
Then again, if you're planning on buying the iPad 2 next year at a discount, it doesn't matter.