It seems iOS 5 is full of hidden "gems" (aka features Apple didn't deem worthy of making publicly available yet), like the earlier panorama camera stitching feature. This time, hacker Sonny Dickson found an Android-like word suggestion bar tucked away in iOS 5. Personally I'm not a huge fan of these, but some people feel it speeds up typing and is helpful. I think it takes up too much real estate and looks clunky.
There are instructions on how to enable this, and just like enabling the panorama mode you'll be using iBackupBot to ensure you don't louse anything up permanently, then editing a plist file in your Library. In our brief testing we found the feature crashed Notes and Mail, and wouldn't show up in Safari, indicating it probably only works in Text Views, not Text Fields (like the Safari URL field).
Neat, but is it really necessary? Let us know in the comments if you'll be enabling this feature on your iPhone or iPad.