Since updating to Froyo, my Samsung Galaxy S freezes periodically and the battery drains far too rapidly. It seems to be draining faster at home where the reception is poor. Thus at night if the phone is not on the charger, I can wake up to a completely drained battery. The freeze can be fixed by removing and reinserting the battery. But this is only a temporary solution.

It seems that the lock-ups happen in areas of poor signal reception. The phone comes factory set to automatically switch between 2G and 3G in order to pick up the best signal. This seems to cause the system to lock-up every so often. The Galaxy S has an option to select either GSM or WCDMA only. I have switched my phone to GSM only and there appears to be some improvement in the battery performance so far, as the phone is no longer constantly searching for a WCDMA signal.
The setting is found at SETTINGS+WIRELESS AND NETWORKS+MOBILE NETWORKS+NETWORK MODE.

There is a hidden menu that accesses the separate bands within both GSM and WCDMA where the user can select the exact reception band required. The hidden menu is found by typing the following on the key pad *#*#197328640#*#* then select DEBUG SCREEN+PHONE CONTROL+NETWORK CONTROL+BAND SELECTION.