I think others have covered one primary concern with the Mu: certain custom parts and Big Unfeeling Company style support. Though the custom parts aren't nearly as problematic as on certain other folding bikes; and Dahon has a good dealer network which does more local support -- at the very least, Thor has a first-rate reputation handling the Dahon complainers on this board. :-) I wouldn't be too worried about getting a Dahon on these grounds.

I should mention that I've been to several Dahon dealers here in Rome (there are three), and have found the same thing: none of them will service the bike. They can't get parts from the company, and Dahon requires them to ship the bike to Dahon. But that's Rome. In the US the situation is much more reasonable.

Likewise others have mentioned that the tikit's front stem is more flexible than the Mu. I don't find that an issue in practice.

I *would* make sure that the bike fits you. Here the tikit shines. The Speed and Mu series have a sort of one-bike-fits-all structure which, if you even moderately tall, will impart an upright feel. The tikit, which comes in three sizes and is *far*more customizable, can easily be set up with a geometry you're used to. The Mu also is a bit squeaky: you'll need to pay close attention to tightening and greasing various latches regularly. (Note: the tikit also requires its own special maintenance).

One honest concern I do have about the Mu is safety. In my experience the Mu (and the Helios before it, of which I have two) has a stem design which tends to slip and rotate on me suddenly: both the handlebar quick-release and particularly the stem telescope, which will pop and rotate about 5 degrees on the Z axis. I'm very surprised Dahon has had this design for so long, since I would think it warranted a safety recall.

The tikit starts at $999. The Mu P24 retails for $949. The P24's big advantage is the DualDrive, which provides a great range at a great price. This is pretty significant. To throw a DualDrive on a tikit runs a good $1700. The Season Tikit (an 8-speed Nexus hub) is $1600.