Hhhhmmm....If you move from 2 to 7, you're going to feel like you've moved from 2 to Photoshop. I haven't used 2 in ages but moving from 4 to 6 took a little getting used to. You can install the new one and leave the old version in place, too. I still have PSE4 on my computer (2 won't work on Vista). The PSE6 and 7 workspaces look completely different - the background is gray. I hated it at first but now I don't even think of it.
What's still the same: The Filters are all still there but the boat on the beach examples are gone. PSE's been using an apple for a few years. The tools are all still there but there are a couple more of them: the Selection Brush and Healing Brushes. There's a Magic Extractor. Photomerge is still there to make panoramas but now there's also Face Merge and a background cleanup tool for montages. There are a number of Smart Objects including Frames which let you make multiple changes to dimensions. There's a Content Palette with Backgrounds, Frames, Specialty Text, Shapes, Themes and Graphics on it. Calendars, Slideshows, etc. are in the Create Workspace. You can't print the Calendars anymore. You have to send them out for printing.... so everyone who made calendars has kept an old version.
The File Browser has been replaced by the Organizer. Once you get used to it, it's easier to use but it's a lot more complicated than the old File Browser.
Oh, when you open the program, it looks a lot like Photoshop. There's no Standard Menu under the Main Menu so you have to use File>Open or the keyboard shortcut instead of the Open icon. The Undo/Redo buttons are still there (Thank Heavens!) and have been moved to the right side, top. There was a lot to get used to but there's so much that's the same that it only took me a couple of weeks to feel really comfortable with the program.
If you add plugins, layer styles, brushes, shapes, etc., you can use those made for the newer versions of Photoshop.
I'd say that if you want to do more and/or do it more easily, then upgrade. But if you're happy where you are with PSE2, then why change?