Am on season three, and I have yet to be bored!
I know the ending re:Trudy's murder plot and such discovered, but I never minded spoilers, and I enjoy getting to know the characters, and the way the mysteries are solved via acute observation!
I know that Sharona (well, the actress playing her) leaves sometime.
I watch on Hulu, and do a split screen--bottom half Monk, top half "junk" e-mails, e-hell, news bolgs, etc...
If I really have to work at the computer, no "TV."