What gmail should offer is a folder system as MSN and Yahoo have. To ignore this is just plain stupid one their part. People are used to have this from Outlook/Thunderbird, why not reproduce that nice, clean environment in a 7Gb mailbox? I know there are filters and labels and stuff, but I just want to be able to put some order in those 5k emails i have...Can't do that with gmail, unfortunately.
Whatever the system is, foldering or labels, it should not break the metaphor of 'folders' as implemented in other systems, including file systems. Gmail does break this metaphor and not with something superior from an ease of use perspective. For example, in the folder scenario, it's one click to see everthing in a folder. Can you say the same for tags? Granted, assigning multiple tags to a single item can be useful, but also confusing and potentially contradictory.
I'm with a folders interface, even if as a metaphor for 'tags'. Or, an improved tags to make them more similar to folders...whatever...just make them easier to use, more informative at the initial level, and quicker to navigate.