My WC app stopped working - no Live tile and the app itself would just display a blank screen with WC logo even after uninstalling and reinstalling. Glad this AccuWeather came along and actually like the look of it better than WC.
I just set up my phone from scratch and had the same problem when I reinstalled the application. If you look at the reviews in the Marketplace, you'll see that it seems quite a few people are experiencing this today.
I never got the live tile to work either. It is definitely more accurate for me but this app doesn't work properly and isn't quite as nice as the webOS version I've seen. Maybe after Mango they will release a revamped 2.0 that isn't so buggy and looks better overall.
I haven't had any issues with it since I installed it. Are those who are having issues certain you haven't started reaching your endpoints limit in your registry?
For some reason whenever the live tile updates, it switches back to Fahrenheit, but upon opening the app and closing it, the live tile switches back to Celsius. It'd be nice if it followed the in app setting and stayed on Celsius.