I just looked into this because I agree, the stock tab is just garbage, no inf, super brief, and takes a long time to update sometimes. I found this though:
http://freewareppc.com/misc/weatherwatchermobile.shtml
Weather Watcher, it's got a gay looking icon, but it works well, allows for any zip/city, has different menus for: now, hourly, daily, detailed, and even a map (map is kinda slow, but whatever) It pulls all weather from the weather channel, which I consider to be pretty darn accurate. and it's pretty detailed.
It doesn't have the tabs at the top like it looks like in that picture, at least not in the "smartphone" version they list in the middle of that page, I haven't tested the main download.
Best part of all of course is FREE!
It doesn't take the place of the weather tab, but it gets dropped right into Programs, and can be assigned to one of the buttons on the Programs page.
But, there's at least one that's decent.