Sidekick II is meant to be your one-stop-shop wireless gadget for e-mailing, web-browsing and IM chatting anywhere you go.  You can also download limited content.  You can also sync with your Outlook calendar and addressbook, but only if you pay extra for a third-party utiltiy program.  Compared to the original Sidekick, SK II is thinner but quite a bit longer.  I also think it's uglier, esp. the new thumb keyboard, but the keyboard is still very useable.  Battery life is terrible after the first couple weeks, requiring you to carry the charger with you all the time.