There are so many things that can be done next. Here's a couple:

• Pull the thumbnails off the camera via USB and make a movie of current progress, like a "time-lapse live-view" :)
  
• Add panning and tilting of the camera so as well as moving sideways, the camera can turn at all sorts of angles during the sequence

If you're interested in more information on building the rail itself there are loads if pictures on Dave Hunt's blog here and here. There's a lot of metalwork involved, though!

Building the motorized rail is certainly worth the effort, though, as the panning effect gives a much more dynamic feeling to the resulting time-lapse sequences.