[magisterludi71]

The connection on my XP/Fusion/OS Xworks fine for a while and then it hangs up for 2-4 minutes. I ran the speed test while it was working fine. I suspect opening a new port or a new browser window can trigger the disconnect (for instance, almost every time I start a SSH session the thing will hang up) but I haven't rigorously followed up on this scenario.
I also looked into the BT PAN, I am reasonably confident that the BT driver on OS X 10.5 is junk. Hopefully the next patch will fix it.