I know this is a tired argument, but I was really hoping this would be addressed with iOS9 and the split-screen multi-tasking. It wasn't. The iPad is still not a laptop replacement, not even for basic tasks like web browsing, chat, and email.
One of the main features of Windows 3.x, and later vastly improved in Windows 95, was scalable windows. This feature was also one the main selling points of OS X - truly scalable vector-based graphics. The ability to arrange windows based on a users needs is very powerful.
This is the scenario: Check my email, see there is a new email with link to a website, open the website, compose a reply email while quoting from the website, send a quick IM to someone asking timing for plans later, reference their response in the email I am still composing, and send the email. This is super basic.
On Windows / OSX / ChromeOS: this is very easy to do. I used to take it for granted, until I tried doing this on iOS. There are very few steps. The only unintuitive step is probably arranging the windows to fit both a browser window and the email compose window at the same time, but really this takes 1 second. Everything else is totally pain free.
On iOS for iPad: this simple everyday task is a total mess.
Starting with the just the first part, open email, click on link in email, which opens safari. Then you swipe from the right to bring up multitasking, which will load your last used split-screen app, then swipe from the top of that to change it to email, then bring the center divider to the center to get some usable space for both, and begin typing your response. You need at least 4 actions to set up the work space.
Then, here is the rub, if you clicked on a link in Mail to open Safari, and brought in Mail again as a split-screen app, it's arranged with Safari on the left (primary) and Mail on the right (secondary). This means to keep Mail open to but swap-out Safari for an IM client, you have to get Mail in the primary side, by dragging the center divider all the way to the left, then swiping from the right to open up the split-screen view again which will bring up Safari as the most recent app, then swiping from the top to bring up the selector menu and pick your IM client. That's another 4 actions just to IM!
Unless of course the IM client hasn't been updated to support split-screen yet, because for some asinine reason Apple requires developers to make this update even if they already have a universal app with all the iPhone-scale graphics in there.
So basically, any sort of use case involving viewing a website, emailing, and IMing at the same time is like playing Fruit Ninja on iOS.