The 450D is much older, and can't really be compared to a newly released camera like the A500. In which - the A500 will be better spec'd and will be better in performance.
Even as a proponent of Inbody IS - I think in lens IS has its advantages. Besides doing its job well. I've used lens IS before and the floating, stabalised view is impressive, though i've got the feeling that it would get me lazy sometimes, but it's easier to compose especially if you are using long lenses.
The greatest boon of in body IS is that they are usable on almost any lens out there. The ability to effectively use vintage and third party lenses is a big boon to many people - and especially useful to people who want good but old glasses, but at the same time don't want to break their piggy banks.
Going in lens IS does get people hooked to the IS enabled lenses, and leave some people hanging elsewhere with no IS at all - if they can't afford it and have to settle for old/vintage or third party.
As a user of older lenses, I think it's has greatly benefitted me, I think that is the greatest boon to go into Systems with inbody IS, and if the accompanying cameras are egronomically sound and provides decent photos, I'd recommend the system readily (and that is Sony)
