I think that you will find the thread that Flutterby directed to you to be most useful and informative.
But to briefly summarize:
PhotoSpark is not a replacement for Scrapbook MAX! - it is a new and separate product marketed by Indigo Rose to extend our audience to include those who may not consider themselves to be "scrapbookers" per se, but who love playing with their digital photographs. Each product has its own community forums - you are welcome to participate in both, but don't worry, you are not being asked to "switch" or anything like that!
PhotoSpark was inspired by Scrapbook MAX! and thus has a very similar design space. The chief difference is the content style. We expect that Scrapbook MAX!-ers will be interested in PhotoSpark mainly for the content that is included (you can use it in Scrapbook MAX! with the free file converter we've made available), or as a gift for the digital enthusiast on your list.
Hope that this and the other thread that Flutterby directed you to answers your questions about our new product!