Updated my XP to the newer firmware 2 days ago and haven't found any signal issues yet. In fact I think the battery usage on cell standby has improved a lot. For the first time in 1 month of usage my XP lasted a full 18hrs of moderate usage, which includes browsing in 2G for some 20 mins and some 4 races in NFS shift
. Display was ON for 1hr 30mins. Still I have 37% left. I think that's a definite improvement.
PS: Update was done using Sony update service tool and not using PC companion. PC companion was stuck at the 'preparing update' section for some 45 mins. So I cancelled it and updated using update service, without a full wipe keeping all user data.