Interesting post, Will. Personally, I find that showing what I'm working on often is key to moving quickly on projects. Also usually avoids the 'I don't like it' point as the design grows on the client. Kind of like a soft introduction.
I usually share at least once a day to show progress, keep me accountable and keep feedback flowing fast. No use in getting precious about your design either, as if there's something I haven't seen/noticed I want to know about it asap :)
I couldn't agree more about not being precious. If you feel an idea has run it's course and it doesn't work then move on. I suppose my reluctance to share too soon is having an idea shot down before you can find it's real potential. I work for a start up, we're building on the same product each day. I like to produce really left field work first and rein it back to something a little more straightforward. If I shared straight away, I think I'd lose my colleague's confidence. I think when producing work for clients it's great to do daily updates to maintain confidence in what you're doing, however that doesn't always have to be visual.