I rather like that nice feeling of building tension. Especially in fics like Maya's "Underwater Light", even if she posts the chapters at a complete random time, and usually without a notice beforehand.

WIPs tend to leave a person with a "more" flavour, and that is their best trait IMHO. Worst thing is, of course, the randomness. Although I know of some WIPs which are getting posted at a regular time. :)