MSilvia:
No, but if you regularly dive in conditions that most benefit from using one, it might make the experience more enjoyable for you.
Please, please, please don't take this as me trying to be a smartass, but what conditions? I think that's what confuses me most of all. I'd appreciate input...
No problem, I'm happy to explain myself. I think most knowledgeable folks would agree that it's a great platform for technical, overhead, and doubles diving, but that aside, it's excellent for cold water recreational divers.
As a newbie diving in New England with a 7mm farmer john and jacket with a jacket BC and AL80, I needed 38 lbs. of lead on my belt. Let me tell you, that sucks to carry around, and it's not easy to find a jacket with integrated weight pockets that can carry that much lead. It pretty much meant wearing a belt, and with 38 lbs on a belt, you end up pretty vertical in the water. I moved some weight from the belt to my cam strap, and that helped some, but it was still not quite what I'd like.
Fast forward several hundred dives, and I could dive that same gear with probably 34 lbs on my belt, but I don't. I got a drysuit, and that let me shave off a few pounds (in addition to it's other benefits). Unfortunately, the DiveRite Transpac II I was using at the time had a chest strap that interfered with the inflator valve on my drysuit, and I was starting to grow frustrated with it. I noticed several of my dive buddies switching to backplates, and I tried one out.
I got a 6 lb steel backplate, a 4 lb single tank adapter, and steel tanks, and suddenly found I was able to dive with only 14 pounds on my belt. I had much better control of my trim due to the better distribution of ballast too. I've found plenty of other reasons to prefer that setup since then, but after the first few dives, I knew I'd never go back to a jacket BC and 10 lbs of extra lead. That it was easy to pack and let let me dive on vacation with no weight belt whatsoever was just icing on the cake, as was the fact that it saved me from having to once again change all my gear when I started to pursue technical training in steel doubles.