SparrowMailApp is actually a functional mail application both on the OSX desktop and iOS iPhone. The key, however, is that it is a standalone and it simply does not integrate well.On the desktop, unlike MailplaneApp, it downloads an caches all sorts of data even though it’s using IMAP. And if you have one of those new MacBook Air laptops then you probably do not have enough disk space and/or the sync process when you use multiple computers is just silliness. Also, if you use GMail heavily, as I do, then you probably also use google voice which unless you have unlimited minutes on your phone you’ll need google chat in order to use your computer as the endpoint.The iPhone app is another nice try if you use it as a standalone. (a) it does not use notifications (b) it does not check your email in the background (c) it does not integrate into other applications like Instapaper in order to email links or texts. There are some workarounds like Prowl and BoxCar but after using it for a day with Prowl it felt klunky and I’ve restored the default MailApp. Part of the problem here is going to be Apple’s security and sandbox policy. I hope that this is not simply a developer problem.I’m waiting for my updates.