I have os4on my iPhone 4its impressive not crazy impressive. The iPad can definitely benefit like folders hasty says it's not the best folder system i have seen but does tidy things up. And the "multi-tasking" or rightfully called "fast app switching" us nice the iPad half does this already by saving everything it does in the apps. The only gain we will get on the iPad is the double home tap and you can swipe thru all the open apps. You can already listen to music on your iPod and do annoying you want on the iPad.
And the os 4 problems are more on the iPhones fault if there are any REAL fault. I believe people just like to complain.