Worse might be a little harsh, but my system:

•Packs slightly more bits into the string (naturally there's a tradeoff with data fidelity) for shorter strings

•Follows a completely logical alphanumeric distribution (Geohash will skip letters, some for good reason, like o and l, and some for not-so-much, like a)

•Some of the other benefits in the original post are also missing.

You could probably do this with other systems, but the goal is to allow everyday people to be able to pack a short string in a tweet and have everybody else know exactly where they mean.