A suggestion - since the windows app is based on a framework that apparently has it's limitations in performance (http://help.doit.im/topics/357), why not use the speedy smooth web version, in the browser, with local storage and offline editing? Google docs style.

Using a framework on windows has the benefit that it's easier to support that platform this way than to write real, native-native code using some ages-old windows libs which would skyrocket the cost of code development and maintenance.

The thing is, I guess most of doit.im users are smartphone (android, iphone) and web based. The most feature rich and the best developed version is the web version. And it runs smooth and nice in the modern browsers. My experience - it's butter in IE10 on a windows 8 tablet. The native windows version if far from running as nice as the web version.

Why not leverage the capabilities of the web-app by adding some HTML5 features to it, like local storage and offline editing?

Local storage would allow web version of doit.im be used without an internet connection, as a "native" app running on the browser engine, but written in plain web language, one version to rule them all - be it mac, be it windows or linux, be it chrome, safari, firefox or IE. Now, admittedly there are always issues with browser specific implementations of HTML5 features, but they're way easier to cover than write native code and if you could cover just chrome and firefox for sure and the rest as "should be fine", that would be probably most of your users covered for sure.

If you can work in the web version, say as a chrome or IE10 tab, offline, do some stuff and then just have it synced between the browser's local storage and doit.im server, the one and actually only problem with using the web version would disappear - the need for a connection. If you can work offline, on any desktop OS, just keeping a single browser tab open with doit.im, you won't really see a difference between a native app and offline web app - maybe except, the offline web app would have all the features and capabilities.

The issue of syncing should be "easy" to tackle, since you already have a bunch of clients on various platforms, contacting the server, so I presume you've got that syncing code in Java (android), Cocoa (iOS), something on mac and windows, so this should be much easier than writing from scratch, since it's been done a few times already. I also guess the most of your engineers use web languages.

This also addresses the issue of a windows 8 metro app. Arguably, some people would prefer a metro app (fullscreen, working nice with touch), on the other hand - some would prefer a classic, desktop app that can be snapped to half screen for multitasking and does a great job with keyboard shortcuts. Well, web version of doit.im with offline storage and editing could be used as both, at the same time - following again this completely subjective example of a windows 8 tablet, just open doit.im in metro IE10 to have a metro butter smooth "native" app, or do the same thing in desktop chrome and you've got yourself a more classic variant.

The same goes for linux app, and really for supporting a wide and coherent set of features on a number of platforms, which is always a pain in the neck.

Now, I do realize you've put time and effort into creating the native apps for mac and windows, so the reasoning among some of you might be - "we've went so far already, are we now to leave it all and head back to the web?". It's actually a faulty reasoning - just because something has been performed for a long time, does not mean continuing it is the best solution. Being consequent is not equivalent to being smart. I'd say a solution which provides the most feauture rich and the smoothest experience for your users, with the least code development and maintenance, is the smarter one.

Web apps, HTML5, local storage, this is where all it's heading. Even MS office, with the 2013 release, is now cloudy, with web apps which are pretty nice and integrate seamlessly into the experience. If such a dinosaur as Microsoft actually bets it's time and money on the cloud subscription model, this should be a reason to think for everybody. They're playing catch-up in some regards with Google Docs. MS has been spending lots of time developing it's native apps that they didn't see that someone came in with a web solution that later on evolved to be usable offline, at which point it started to pose a serious threat to MS business model.

So I suggest you take advantage of your competition by supporting a number of platforms they never will with a coherent set of features in an offline-capable web version, something which is practically impossible by native app approach that some people still believe..

One last remark - this whole thing is not as much of an issue from the point of view of someone sitting in front of a standard, desktop PC (I mean big box, external monitor, cable connection, etc). If you're using doit.im on a desktop, you won't feel this. But if you're mobile, using doit.im on an ultrabook or my case - windows 8 hybrid tablet/laptop, then sometimes you've got wifi, but sometimes you're mobile. Nevertheless, you always want doit.im up and running whenever you feel like doing something with your favourite GTD app.