I think that to the portion of Fast's clientele that had no interest in SharePoint it may be an annoyance (that may be an understatement). Doubly so for any of them running it on something other than Windows. For the rest of us, though, it is supposed to be an easy path to a high quality enterprise search engine. It's funny, though, because I have been a proponent of SharePoint as a very good poor man's enterprise search engine. SharePoint 2007 search works well. Yes, it is a bit quirky, but it is pretty powerful. It has served us well (though not as an enterprise search engine, just for SharePoint search).
Microsoft isn't content to stand still, though, so they have added this great option. I have not worked with even a beta or demo of the product, and as far as I know, pricing has yet to be released, so my impressions are based on fairly thin marketing vapor, but it's still OK to start thinking about what it all means.
One would expect this product to scale better than OOTB SharePoint 2007 search, but I wonder if the this is really the case. After all, if you implement this product you probably will be taking it more seriously and devote more resources to it, so THAT will make it scale better too. Old SharePoint search can be scaled quite large without having to resort to anything magical. A million or two documents is a piece of cake.
But I would expect the product to deliver better relevance, with or without active intervention. I am anxious to seek how well search librarian tasks can be delegated - this is important functionality.
Unified installation doesn't look like it is really coming in 2010. From what I've heard, it may be in the same box (or on the same box) but the code base isn't really all that close to SharePoint. Unified administration, on the other hand looks like it IS in the box. But like I said earlier, administration needs to be distributable (think "librarians").
Soon it will be time to stop thinking about possibilities and testing the release product to see how it meets these expectations. Fast in SharePoint may democratizes enterprise search, but a lot will depend on pricing. Soon we will see!