I've been using "No Folder" as my Inbox... which has been working great, but lacks the class of seeing it explicitly labeled Inbox.
The solution? I have a saved search for "No Folder" that I have saved with the name "Inbox". :P
If the future holds improvements to the search page (such as specifying one thing OR another) I will also add: OR tag = "No Tag"... OR goal = "No Goal"... so I have one place to check for all things that still need processing. Since, after all, that's what an Inbox is: it's the pile of stuff that isn't processed.