If I do have one complaint, it's the keyboard layout. Annoyingly the Internet Explorer button is next to the (somewhat short) Spacebar - the result is that while you're in the middle of typing a sentence, Internet Explorer fires up and you're presented with the Orange World home page. After a while I taught myself to be more accurate when striking the Spacebar, but it still may have been prudent to place a different button next to it.
But you don't always need to use a keyboard while you're out and about. Sometimes a portrait aspect ratio handheld device can be easier - but don't worry, the M5000 has that covered.
The screen on the M5000 will swivel around to face outwards and then fold flat against the keyboard. Once you do this the screen layout automatically switches from landscape to portrait mode. You can then use the M5000 like any normal PDA.
But let's not forget that this is a connected device so you can also use it as a phone. As always with PDA/phone hybrids, I can't help but feel ridiculous holding something the size of a sandwich up to my head and talking into it. But the point is that the functionality is there if you need it.
For me the real advantage to having a SIM in a device like this is the data options that you have at your disposal. Once you get used to having a fast, connected device in your pocket (albeit a large pocket) you'll never want to go back. Note the word "fast" in the previous sentence - there are a lot of connected PDA devices out there but almost all of them are GPRS based rather than 3G.