Gmail tags are awesome. They just need better tools to automatically tag emails as they come in.
When Google released Gmail, it didn't have folders; it had tags. For some people this was considered crazy, because they were so accustomed to the idea of putting things into folders that they couldn't even consider an email system without them.
Eventually people learned that unlike placing an email into one folder, they could tag any given email with as many tag names as they want, making it easy to find an email that fit more than one category.
For example, if you received an email with a proposal from a client who is waiting for a reply, you might tag that email as:
Clients... because it's a client.
Proposals... because it's a proposal.
Pending... because you are still... [More]
Continue...Smart Tags in Gmail...