I hope 4.1 fixes the issues people are having. I have read that 4.1 also fixes the bluetooth problems as well. In my mind, Apple knows there are problems, and if they cared about there customers as much they claim, they would release a 4.0.x release to fix the issues people are having. Mid to late September is unacceptable. The iPod event is not going to be any less exciting and newsworthy if they released the proximity sensor and bluetooth fixes now.
I have patiently waited for a fix that never seems to come and have restored my phone several times and reset network settings for temporary relief, but I have had enough. I spoke to Apple support today and set up an appointment with a Genius for Wednesday. The Apple rep was willing to do an advanced replacement, but I knew I would be near the Apple store. Some folks are reporting getting an iPhone free of issues. Not even sure if it is worth exchanging, but at this point, it's worth it to me to try.