iOS 8 doesn't make a huge difference, visually, save a few small points.
In case you've been so content with your iPad 2 over the last few years that you've drifted away from paying attention to the Apple product cycle, here is some six-month-old news: Apple finally stopped selling the iPad 2 model back in March. After it hung on at the bottom of the tablet product line for a couple of years to be a rock for the education and corporate markets, Apple kicked the iPad 2 out and resurrected the iPad 4 as the new full-size budget model.
But for now, Apple is continuing to update the iPad 2, in part because it has so much in common with the non-retina iPad mini, including the Apple A5 processor and 1024x768 display. But the iPad 2 hung around so long because it's also a legacy device. There are students depending on updates, as well as companies who used the iPad as a default device, like Square.
iOS 7 didn't do a whole lot of damage to the iPad 2, and even improved it in some aspects, like how fast the browser could load webpages. But this time around, the new version of iOS 8 appears to make the start of a much bigger decline, not only in performance, but in appearance.