General impressions of the new Canon 50D and high ISOs are that 3200 is very good if you are spot on with the exposure. Naturally, underexposure will bring out noise but that is true at any ISO. ISO6400 is useable and ISO12800 will be reserved for emergencies only when it means the difference between getting the shot or not.
Now for the Canon 18-200 f/3.5-5.6 IS lens - it is a good walk-around, general purpose lens. However, I've worked hard to acquire my current lens line-up and each lens serves a purpose so I think I will sell this lens.
Now back to sorting images from yesterday. I'll post a link soon.