Upload & Sell: On
Are you ready to change lenses? The OM-D is a fantastic camera, though to use your existing lenses, you'd need to also get the 4/3 to Micro 4/3 adapter, and most lenses won't autofocus as fast as they do on your E-620.
That said, the native Micro 4/3 lenses will autofocus blazingly fast, and are also very good lenses. Depending on what lenses you own already, some may be worth hanging on to to use with the OM-D and adapter.
The in-body IS is a whole new level of stabilization from Olympus' earlier IBIS systems...much more stable, in-viewfinder stability, etc.
If you click the WWW button on my post, my site has a lot of reviews of Micro 4/3 cameras and lenses, including the OM-D.