I agree with many of the opinions posted in this thread so far. For me personally, it was a nice challenge to try and climb the old leaderboard and I like checking it for that reason. With the new system being able to advance will likely become more of a time than a skill challenge to players, which I think is not an improvement.
I also think that the leaderboard is mainly meant to give an idea about the skill of your opponent, in case you never played or heard of him. The new system will not do such a good job of this, unless you and your partner are both really active players. For example, if you look at today's leaderboard, shark_bait is Level 13 and in my opinion he's one of the best players, if you judge it by his success in the two Isodom tournaments. He just doesn't play a lot and with only 22 of his games counting, TrueSkill can't rank him higher.
I know that there are probably many ideas on how to improve the leaderboard and I think it's great that dougz has tried something new and you can always go back (which I would also encourage for the recent update).
An idea I had for a while was that the leaderboard could show your skill among the players that are actually listed. I think everyone agrees that it makes sense not to list players after they have been inactive for a while. Some of these players will come back and some of them never do. So what if the leaderboard would count all of your games (like in the old leaderboard) but only against players that were active in the past X days. I don't know how much longer it would take to update the leaderboard in such a way, but if it's easy to implement, I would really like to see the results. This would be a way to show your skill as it compares to the active community. It's just a question how you would define "active" in that case. If you use X=30 days for this method it probably won't change the old leaderboard too much.
Anyways, this is a good discussion, I hope the outcome will be as well