There are a couple of other options for purchasing Smart Pianosoft and Pianosoft titles (many of them dropped from Yamaha's store site). Right now EastCoastMusic dot com is running their 10 year anniversary sale with free shipping. Just type in Pianosoft in the search box. They also have a decent selection of Pianosoft + Audio which has the original artists accompanied by the Disklavier all on one CD. I really like: "The Tracks of My Tears" - "David Garfield and the Monster Trio" and all of the Sue Downs and Mike Garson CDs.
Other options are: sheetmusicplus, halleonard, & music44. Yamahamusicsoft site has 20% off sales throughout the year (usually around holidays), and they do let you download some Pianosoft titles (which saves in shipping and waiting time).
Also search this site for help on getting your Smart-Pianosoft floppies to play with the commercial CDs. Keep in mind that you MUST purchase the EXACT matching CD catalog number listed on the front of the SmartPianoSoft package. As CDs albums often get reissued or change distributors the piano accompaniment on your Disklavier may not play at all if the CD is not the exact match.