It doesn't seem to support priority inbox, which is critical to my workflow. My currently gmail inbox looks like this:
in:inbox is:important is:unread
in:inbox -l:important -is:updates -is:promotions -is:social
in:inbox -l:important (is:updates OR is:social)
in:inbox -l:important is:promotions
in:inbox is:important is:read
The only reason it's like that is because gmail limits you to five sections. Ideally I would split up updates and social.
The first section is my triage section, and the only one whose unread count I care about. The rest I try to triage by skimming once a day and cleaning once a week.
Then the last section is my "todo" section, things I have to respond to that will take more than a minute.
So if I could customize the interface with the searches I want and in the order I want, that would be ideal. And then have a view where I can select how many messages from each section are visible at once (like in Gmail's multiple inbox view).
If I could do that, I could easily see myself paying $100 for that, especially if it has a companion ipad/iphone app.