So, I haven't upgraded firmware yet as I'm at work. But I just did a couple of speed tests.
Phone on table, 5 bars of 3G signal:
Download 2.08 mbps
Upload 1.54 mbps
Phone in hand, full on death grip for 2 mins prior, with 1 bar 3G showing:
Download 2.09 mbps
Upload 1.21 mbps
I did four or five death grip tets back to back all with pretty much the same results.
So I then did another full bars test with phone on the table and got:
Download 2.80 mbps
Upload 1.53 mbps
And then went back to another death grip test, this time with:
Download 0.15 mbps
Upload 0.17 mbps
Did a couple more of these, and releasing the phone mid test would see figures jump up suddenly before test was over, so clearly signal being blocked.
Not really sure what to make of that. First indication was regardless of the bars I was getting roughly the same results, second test shows that death grip was indeed a death grip!
I think this is my long winded way of saying I do not think this new firmware will 'really' do much other than have a placebo effect.
Either way, I love my iP4 and the signal issue has never once ruined my use of the phone in normal conditions.