I came from the Galaxy S to the Bionic. I actually upgraded to the Bionic because it was being discontinued and was free ($30 upgrade fee of course). I also wanted to keep my unlimited plan on a 4g phone. It was a major upgrade even with Gingerbread on it. My wife ended up getting the same phone and she loves it and isn't very techy. ICS brought this phone to a whole new level. The icing on the cake for me is the lapdock. It's a shame the lapdocks were discontinued but at $300 they were never priced to succeed. I'm quite pleased with the Bionic and I'm looking forward to Jellybean.
On another note, The galaxy S was the best phone I owned before this one. Before that I came from BB Storm. The Storm was an upgrade to older BB phones but the OS was very buggy. I was pleased with the Galaxy S even on Eclair after the BB. Froyo was a nice upgrade and the G-Bread so the Galaxy S kept improving.
I intend to hold onto the Bionic for as long as possible or if it becomes obsolete because of newer technology. At this time, there really isn't anything else I would want if I could have it.