Just a heads up that $45 is steep for what others do free or for less money is somewhat an errant assumption, as in my experience I haven't found anything close to evernote yet. Evernote's synching isn't quite the same as simplenote or taskpaper, synching just to the server or manually synching just text notes to a few pc's. Evernote automatically synchs our notebooks (and new notes) within minutes to: a Mac, powerbook, Windows Vista, two ipads, two iphones, Windows XP, and a Fujitsue Tablet PC, without us really having to do anything. Plus we have access to all of it via the web.
Not only does it synch notes, but we attache spreadsheets, word docs, pictures, capture web page clippings (graphics, text, layout), PDFs, etc.. I can't tell you how many times we have saved time and effort using this feature. Could dropbox/box.net do something similar with these type of files? Close, but why have a place for notes, a place for files, etc. and dropbox/box don't allow for tagging, searching along with notes, etc.
And premium also gets you SSL everywhere, which I am not sure simplenote/taskpaper does.
You may be able to cobble together several apps and services to do something akin to what Evernote does, but it won't be as easy, your stuff will be spread around, you won't have some of the capabilities. $45 isn't much to pay for the convenience of "it just works" that evernote at least provides us.