GeorgeCT,
Yeah, they're calling it the TSU99A.X, retail $30, available for more like $21. Still a good bit more than the 528MP at Lowe's. It really is, for the most part, exactly the same valve. To ensure that the settings are uber-precisely-what-they-were-in-the-factory, they give you detailed instructions. They provide a table that shows how many "pegs" high to set the valve (i.e. tank refill level), for each and every Toto toilet, and then instruct you to install the "tamper-proof key" so the valve can't be set to use more water (unless you just peel off the key). Generally, nobody uses that key with the 528, but I guess it's a good way to ensure that the thing stays set exactly the way they would set it at the factory. They also give you this gizmo that adjusts the refill percentage to exactly what it was on the original valve being replaced, rather than the "eyeball it" method that most people use with the 528MP. For anybody who is handy, and who doesn't mind experimenting a bit to get the water level and refill where they should be, all you need is the 528MP. I do respect Toto, however, for trying to make sure that any replacement valve will provide the same level of water savings that came with the toilet.
All-in-all, it's a pretty-smart idea by Toto, and I appreciate their level of precision in foolproofing the settings. One valve on the shelf at the plumbing supply, instead of 20 different types. And it's a Made in US product. Of course, Terry was telling people to do this pretty much as soon as the 582MP came out. Toto finally caught on.