This has no OS (at least that you can access). I have one, have written a number of drafts with it, and regret both purchasing it and it not being a better machine. The software is really bad and there is no way to tinker with it, no way to write custom software. Indeed, in the last update before it became abandonware, they made updates cryptographically signed to make it more difficult for people to jailbreak it. The hardware is pretty and the keyboard is nice but the battery is really bad. It lasts only a few hours and takes forever to charge. And if the battery is depleted, it takes too long to get to the charge level necessary for using it even while plugged. Please don't buy this.
I have one of these sitting next to me right now, and it's essentially unusable due to the dispaly lag, and largely (though not completely) reliant on a service from the vendor for syncing. The hardware is passable, but the software is not, and it seems to be at a very slow drip of maintenance, if not completely abandoned.
The screen and battery are too small; you really want a laptop or subnotebook form factor where the screen opens like a book so screen and keyboard can both be large enough to be useful.
A5 format (like a book, slightly less than most laptops) seems a sweet spot, also for keeping it in a larger jacket pocket.