Apparently they are going to fix the signal issue with a firmware upgrade. ie make the signal bar look like you've got better reception than you have, so the blame for dropped calls is dumped on service providers. They said it was a hardware issue, now it can suddenly be fixed by software update. I love the phone but it is so stupid it has this problem, I think perhaps Apple seeing what they can get away with now that they're the biggest technology company in the world now. I was going to buy the bumper anyway (usually avoid cases at all cost, but apples own case for it...it's good) before the signal issue even arose, so it doesn't make that much difference to my life. Rant over...
I think you have misunderstood, it's to do with the lag swapping between frequencies etc causing the signal to drop they are not going to make it show a better signal than is actually available that's ridiculous, the software update will solve the problem, not mask it.
More evidence for the fact it is software not hardware is the fact people who have updated to OS4 on the 3GS have reported similar signal problems (check the macrumors forum).
There's a post on appleinsider explaining it all in detail, go read it.
I'd still use a case anyway, daft not to on a £500+ phone, even if your the most careful person in the world all it takes is a slip and a bad fall. It still looks awesome in a case especially that armor case that you can hardly tell is there