I think it would be very cool to be able to visit and track these interstellar craft (especially following them with accellerated time and see which systems they get close to - not sure if Celestia takes account of rotation of the Milky Way, gravity etc...) either way it would be nice!
Also, my 3 year old son and I would like to thank the creators and contributors of this wonderful program, which we have only just discovered...

enabling non-mega rich ordinary folk to soar among the stars as virtual space tourists, in a small way you have fulfilled a lifelong ambition of mine and will fill my boy's head with wonder... the Open Source community Rocks! Keep up the superb work