Well, I'll be a bit of dissenting voice here. I *hate* carrying tripods around. Thus I have become exclusively a hand-held shooter. And yes, I still get a lot of tack-sharp images. Even at shutter times of MUCH longer than 1/FL.
Many of my lenses have IS and I have learned techniques for successful handheld shooting. Years of experience in shooting handguns helps here. Same things apply; I often hit bullseyes at distances others have trouble hitting the target at all.
Pull your elbows in to your body. Take a relatively deep breath. Let it out and try to achieve a state of momentary calm. Roll your finger onto the shutter button, almost to the point where you can't quite tell exactly when the camera is going to shoot. If you end up taking two or three frames because the camera repeat rate is fast, chances are very good one will be sharp. If shooting multiples bothers you, set the camera for single shot mode.
When you get good at the above you can learn to time your shots to be between your heart beats. I do it all the time.
And don't be afraid or embarrassed to brace your arms or hands on something solid - e.g. a railing or branch - if it's available.
Actively think about keeping steady while shooting; do it for a week, and it will become habit. Then you can bank on getting sharp images handheld. You'll be surprised at how sharp.
Handheld shooting rules!
-Noel
P.S., Here's one of quite a number of sharp handheld wildlife shots I captured last weekend. I was standing and braced on nothing for this shot, which is 1/100 sec at 400mm (Canon 100-400 IS zoom):
http://forum.ourdarkskies.com/galler..._16_635563.jpg 
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