While there are certain areas that I don't push myself (for example, I don't bungee jump) I've always thought it a good idea to push the limits of hobbies, especially the slow-speed stuff.
I purchased a used tripod head (Bogen 3055) and decided to take it out to Golden Gate park to do some slow shooting. The combination on the camera for the above shot was the 100-400 IS Canon lens, a 1.4 teleconverter, and a 21mm extension tube at the camera body. With this setup, I was manually focusing at something around f.10, working with a very small depth of field because of the extension tube, and dealing with a bird that liked to move a lot. Thankfully this was not a hummingbird, that would have been impossible.
The nice thing about using the extension tube on top of the 100-400 and 1.4x teleconverter is that it does change the depth of field. It pulls in the focusing points so that you can focus closer, but you can't focus to infinity. If I wasn't shooting with the extension tube, I believe the depth of field in this shot would have been deeper, and therefore more distracting.
End result is, I personally need to get out and play with my gear to see what it does, and what combinations of things work under what circumstances.