For me at least I prefer committing at the end of the day but I can see the appeal of only committing once a feature etc has been completed. However, I would suggest this is bad due to the progress you make as you get to that solution/new feature.
It's also easier for me to at the end of the day as I change machines - so by necessity, I have to commit all the time to continue development.
I'd say the tl;dr is commit when something meaningful has been done, useful information has been added and/or through necessity (such as moving machines).

Depends a lot, if I'm fixing bugs or something I started committing everything when all bugs were fixed or when the day ended. Now I'm committing every time a single bug is fixed. When developing I start committing when structure is done, when a specific function has been done, when style of a section is done and so on, specially when I think I could fok something up.

for me it varies, one thing i started to do, is to write commit messages like "when applied this commit will ....." git can handle a lot of small commits SVN on the other hand does not care that much.

For me the more important part is the branching since I mainly use git :)

For every meaningful change, there's a commit if all tests still pass.