I've got a program which is continuously squirting a new set of 60 RGB values to the blinky tape and then sending the "update" code (255). My problem is that this runs at about 30Hz for a while and then after a few minutes of doing this drops down to about 1Hz. After this has happened I generally need to power-cycle the binkytape to get it back to the 30Hz performance. Occasionally it will fix itself after a few minutes of the slow performance. Having instrumented my code with some timers, its definately the serial write which is slowing things down.
This is using the default firmware and happens if I drive the tape from either a linux box or a Mac.