There is a great tutorial of Muse at Lynda.com, though it costs $25/month to join. I join Lynda.com for a month or two a year, just to get an idea of what is out there, and I saw that Muse really is doable for me. There is something intuitive about Muse, that makes it attractive to me.
But, when it gets out of beta there may be a lot of catches...and I am really locked into the Apple platform.
I think for those Adobe fans out there, who love Photoshop, Premiere Pro etc, then Muse will be a great addition and they won't mind the monthly charge of $50. I did check with Adobe and was told that the $600 yearly fee got you the right to put up only one site, and the details of the entire suite were still being worked out.
Me, I can't afford the cost.
But personally, looking at muse as a standalone application, it looks like fun.
I have seen several reports from developers who have the next version of OSX, who say it works fine with iWeb (hope that last isn't a violation of Apple's regs). So it could be that people could be able to use iWeb for years to come, like many people are using iMovie HD 06, and loving it. Not sure how iWeb sites are making the transition to the mobile ipad/iphone world though.
Hugh