I use the USB cable between the computer and my Optimus S frequently because the throughput is better than using the WiFi hotspot feature.
On occasion with 2.2.2, I would disconnect but the phone would not return the network connection to its previous state and mobile applications were unable to use the EVDO network at all. I could re-connect from the computer and disconnect and everything was fine again. It was an inconvenience.
Since 2.3.3, this seems to be the case the majority of the time, and my workaround no longer works. I must power cycle the phone to regain control. I appreciate the new icon to show the connection, as it's easier to realize that the problem exists.
I'm glad to have the upgrade. I just hope that problems like this one will be fixed. The WiFi hotspot performs better with 2.3.3 but it still lags a lot compared to the wired connection.
Since I've been using the hotspot more, it's been failing, also. It almost looks like an automatic setting to prevent being online while idle but when I'm idle, I'm not online. I shut it off.
The hotspot wasn't very reliable in 2.2.2 but it's less stable now, even if it is faster.