This isn't surprising. In revising iOS devices every year, Apple can't deliver a must-upgrade every year. Even if they could, they can't. There are a tangle of marketing issues. You want to ship something that will entice people who don't own a tablet to buy an iPad, get people who bought into Android early to switch, and make incremental steps in improving platform performance and features to lay groundwork for new, more powerful and unique "must-have" apps and iOS features that may not launch a year or more from now.
You don't want to ship something that makes people who spent $500+ on an iPad not even just a whole year ago, but perhaps around the 2010 holidays, feel like they've in any way been left behind and must upgrade for their iPad to remain useful. Make people feel like they wasted their money a few months ago and they'll drop out of the tablet market or switch to a tablet product they feel has longer legs, that they feel will readily last them at least two and preferably three years without virtually demanding an upgrade.
Look at iPhone. Out of three distinct model updates, the iPhone 4 was really the first "hey, we threw everything into this one and you absolutely must jump on the bandwagon or upgrade now" model. That's a two-year gap with models covering three years. There were incremental feature and performance upgrades in between but the 4 was the heavy hitter. Expect with the iPad, the iPad 3 or 4 will be the first heavy hitter upgrade.
It's all a balancing act, especially if you're selling a lot of media and software for the devices, too. Pull in as many new customers as possible without alienating your base, making them feel forced to upgrade, until they also feel they wrung every dime of worth out of their previous purchase.
Devotee forums don't give the broad perspective that Apple is concerned about in marketing their devices. In general, no one buys a new phone or tablet or laptop or desktop every time a revision is released. Most people go three years or more, depending on the device. But in these sorts of forums, a lot of people do upgrade at every new revision. If your business model relies mostly on current customers upgrading every time there's a new revision to your product, you're either going out of business straightaway or you have a very small customer base.
Nothing odd about not perceiving large performance gains in regular iPad usage with current generation apps. You're not supposed to.