My kit previously was a 350D with kit lenses. I now have 2 7D's, have different budget lenses, as well as a 70-200 f/2.8 and a 50mm f/1.8.
With the 350 I was able to operate in 100 to 400 ISO and get excellent results but most of my work was sports shots so shutter speeds were high.
With the 7D I find I now have to work with a minimum 400ISO to get the same results.
One pice of information I was given by Clubmanmc, to whom I am extremely grateful for his advice, is keep the shutter speed above 1/100th.
Now that I do that I find that my results are consistently good. Don't get me wrong I still have a hell of a lot to learn but with the new gear and due to the Kitesurfing season being over I have moved into other genres so my approach has changed a lot.
As for practice changes, I have had to work very much on my stance and holding the camera. Both are working better together now, so I now find I am a bit more stable. I can't remember who but someone posted a link about holding your camera the other week. I'll find it and post it here.
http://www.youtube.com/watch?v=EDsx3-FWfwk