Some advantages, compare to Rapportive:
1. Works on any site, not only gmail. So you can use it in Facebook, Yahoo mail e.t.c.
2. Supports info not only by email but by any known profile. For example – it’s possible to see who write comments or articles on newspapers, blogs and so on.
3. Full Twitter support. Just try to see how it’s usefull there.
4. All short urls became full on mouse over
5. You can save any contact on any site to your gmail adressbook by one simple click.