Many designers dislike Dribbble because they don't think the shots are "real-world designs." I find Dribbble a very valuable resource and here's why.
Dribbble is a perfect place to:
Observe design trends
Companies and clients don't want their products to look like they were made in the early 90's no matter how great the usability is, unless their brand aesthetic is all about the early 90's!
People see modern designs and like their products to look modern, even though they don't know how to articulate them. Designers need to be sensitive to design trends.
Find visual treatment examples
Sometimes I run into problems styling certain elements on a page. Maybe a form has too many fields, or a table cell has too much text.
I often find it useful to hop on Dribbble and look at how other designers treat certain elements. Perhaps they lighten certain labels or add icons at certain places. It helps me consider options that I haven't thought of.
Be inspired by layout possibilities
Dribbble is a great place to look at a lot of examples all at once. For example, I can search for "Dashboard" and instantly see a ton of different ways to design dashboards -- with different layouts, color schemes or typographical treatments.
I can then take these inspirations and experiment with my own designs and see what works.
Dribbble is not a place to:
Find examples of good usability
Dribbble shots provide very little info on who the customers are, the problems to be solved, or any data on how well the design performs if it's shipped at all. For inspirations on usability, case studies or UX research articles would be more helpful.
Learn about problem-solving process
Again, Dribbble shots do not provide information on how the shots were designed. To learn about the problem-solving process, reading design case studies would be more useful.
Find designs that you can copy and paste into your work
You may look at a Dribbble shot and think, "well, that'd never work with my current project."
And you're right. Nothing will work for your current project unless YOU put in thoughts and efforts to solve the particular problem for the customers.
So there's no point thinking that Dribbble shots are useless because it's not something you can just copy into your work and be great.
So that's my view on Dribbble. I love it, case closed!