Very much so. I had loan of a 100-400 IS, which spent part of the time on each body. And used the 55-250mm on the other one. Whilst it wasn't as quick as the L glass, it did remarkably well, and delivered sharp shots.
The 50D aquired focus quicker, and was better at holding it. We were about 100 metres east of Coode St. What amazed me was one of the photo's on the 50D at a set of pylons I'd guess as being about 700 metres away had recognisable detail in Kings Park, which measures out on the map as being 2 1/2 Km away. Not only was the Queen Victoria statue reasonably sharp (although at F7.1 was out of the DOF), you could make out what colour clothing the audience was wearing, with the Head, torso, and legs recognisable as seperate items, and even made out a child walking/running as you could make out his legs. I was stunned. I'm trying to find my best 40D shot at 400mm of the same Pylons to make comparisons.
Also whilst panning (both set to centre point only), the 50D often lit up focus confirmation on AI servo which the 40D didn't. I'm not sure if that's a software thing, or quicker calculations allowing focus lock to come up.
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The Aussie Viking