Ios5 beta to Ios5 GM has been out to developers since June. Thats almost 5 months of time to make apps work for ios5. There are alot of Apps working on ios5. I'm on Ios5 with around 40 apps I had from 4.3.5 and haven't had issues. From games, to memory apps, to utilities, etc. There is far for than just gamefly optimized for ios5 right now.
1. All the battery apps work
2. All the weather apps work
3. On my phone, I can't account for all of the 200,000 app store apps but I don't have a app not working on Ios5 regardless of it saying it is optimized for ios5.
4. Ios5 will released to the public on the 12th 2 days before the Iphone4S release date. Thats in 4 days. The apps in the app store are ready.
Hope this helps