Sherwood,
I agree Canon L (Luxury) glass is NOT cheap, but in photography you get what you pay for! I bought the 24-70 f/2.8 L and it is the best thing I could have done. Sensors are so advanced now that even entry level models achieve amazing results with good glass.
I took the follow shot on my 450D - bottom of the spec sheet and discontinued 2 years ago.
S
FULL SIZES HERE -
http://www.flickr.com/photos/lampertron/4956143361/sizes/l/in/photostream/
If you look at the 3000px size version, the detail captured by L grade glass is second to none.
I plan on getting a 5D mark II or III (when it finally comes out) and having invested in good glass I know I'll get the best out of whatever body I use.
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On a final note, and no disrespect to the 500D owners, your 50D has one of the best sensors made by Canon and will take phenomenal stills with good glass. No video granted, but for stills you are looking at (best to worse) 1D, 5D,
50D, 7D, 60D, 550D, 1100D.
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My 2 pence................