Celeste is an e-mail reader.  Scamper is a web browser.  Both need
improvement before they are killer apps, though I think some people
ues Celeste every day.  See http://map.squeak.org

Croquet is in some ways a radical rethinking of what the web could be
like.  Sophie is very definitely a radical rethinking of what a book
could be like.  You should take a look at those projects.

Squeak is more likely to attract people by doing something unique like
Croquet or Sophie than by trying to compete with the rest of the world
with e-mail and web browsing.  But, if you can get people to make
Celeste or Scamper good enough that a lot of people use them every
day, more power to you!

-Ralph