Will I need a Magic Trackpad to take advantage of OS X Lion? [closed]

The only thing you wont be able to use, are the Multi-Touch Gestures.

Generally, Stack Exchange network avoids talking about future products, but since Lion is going to be released very soon (according to a lot of sources), and having the GM installed on a computer next to me, I'd say that a multi-touch surface like the Trackpad or the Magic Mouse does add a lot of interesting possibilities to the UI.

If you're a regular OS X user and don't have a magic XXX, you will be able to do the same you do right now, you will be just missing the possibility to perform gestures that simplify your workflow.

I personally cannot get used to it to be honest, but I'm a heavy keyboard oriented user, so the mouse is for those "moments" when the Keyboard doesn't cut it.

I would recommend you go to the nearest Apple store and play with it for a while (i.e. more than 5 minutes). to see if you can get used to the concept of a trackpad surface.