Site Conversion and Outdated Links

How will Google handle this?

[pdivi]

I just converted a site from PHP to ASP. I carefully optimized the new pages, so I think the long-term effect will be positive. But I'm not sure what to expect short-term.

Google has about 50 of my PHP pages indexed, and those pages no longer exist. To keep end-users happy, I put a redirect on the error the old pages generate. But how will Google handle this situation? Will they drop the pages once they find the redirect? Will they pick up the new ASP pages at the same time they find the PHP pages no longer exist? Is there anything I can do to make the transition less harsh?

Thanks in advance.