As a 3.0 user myself I have been affected by some of these, such as the WiFi connectivity issues which have caused hundreds of users problems.
The battery life using 3.0, for some has dropped drastically and I have myself seen a bit of a drop in the batteries performance.
Destructive video editing on the iPhone 3GS. which Apple has fixed in 3.1. Also some unknown problem with 3.0 which causes the device to over heat and the battery to drop drastically as I experienced whilst using Qik to live stream a video.
These are just a few problems that 3.0 users are having and Apple really needs to sort these out, as a lot of people rely on there iPhone to last throughout the day, we don’t want it to be like the Palm Pre do we. Hopefully these will be fixed in 3.1 and anyone using the 3.1 Beta feel free to drop a comment on if any of these problems, or others, have been fixed or even maybe caused by that update.