IMAP is a protocol. It isn't up to you to define how it should be used. It makes an excellent alternative to POP when email is accessed by many different computers.
The way that *I* use IMAP it may as well be POP, if POP was optimized to keep many gigabytes of email available.
Also, the way that I use IMAP, the "server" is an older 1 GHz CPU with 256 MB RAM and a single 5,400 RPM hard disk. All of the machines that I read my email with are far more capable and perform searches much much faster locally.
I find the features of Thunderbird 3 and Evolution to be very useful to me in this situation. These programs and the IMAP protocol work very well for what *I* use it for.