Hi Les...I got the 450D for astrophotography.
As to the reasons why this one? probably best to read here:
http://ghonis2.ho8.com/rebelmod450d1.html
main reasons:
Cost (under $1K with basic 18/55 IS lens); low amp noise; cheap(ish) accessories; easy to front filter mod
; takes RAW pics; Live view (for focus); did I mention cost!; and many others using this camera so I can learn from them.
It's not necessarily the "best" but...you have to pay to get the best. I see it as a good starter, although I'd love a 20Da.
I could not afford the extra $$ for the 40D...as much as it appeals to me