EDIT: Thanks to Oleksandr for pointing out my error on this post. :) I love the photo community on the internet! :)
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We went ice skating recently and the rink has a rule about taking cameras out on the ice. Naturally, this is a rule I completely disregard. :) With that rule in mind I did use my 4th string DSLR...my trusty 4 year old Canon EOS 10D. I love shooting slow shutter of action shots (especially sports and children...bonus when I can combine the two). In order to get the slow shutter I need, I have to stop the aperature way down.

A small aperature can reveal nasty dirt specks on a DSLR sensor at a low / slow shutter speed that a normal or fast shutter speed would not reveal. See below for examples...

sensor specks barely noticeable... (1/45 second, f22, ISO 100)






...dust specks even more noticeable! (1/20 sec, f32, ISO 100)

And here's a fast shutter speed -- same camera and lens. The image below was shot at 1/500 second, f5.6. The sensor was not cleaned for this shot...but you can not see the dust specs.