Sometimes i miss my 5800 for the following reasons:

• Battery Life
  Google Maps
  The ability to automatically connect and diconnect from email account
  The better music player (EQ and stuff, LCG Jukebox with sleeptimer)
  DB Railnavigator
  and some other stuff ic can't reme,ber right now because i have thrown myself into the n900

But to buy the N900 was a very good choice because these things or similiar ones will definetly come with time.