Thanks to the sensor's rechargeable battery and its compatibility with any kind of paper or flat surface, you can use the Mobile Notes pen pretty much anywhere. Portability is not a problem since the sensor is just under 7cm wide and 3cm across, so is perfectly pocketable. To prevent the battery running down, the sensor switches itself off after a period of inactivity.
E-Pens has provided a bulky case for carrying the set around and though it's better than nothing it is not very impressive. It is made from cardboard with a magnetic clasp, while foam cut-out internals protect the pen and sensor. Aside from the case's large size, the major annoyance is that it doesn't provide any cut-outs for spare pen batteries or, more importantly, for the spare nib. Depending on usage you might want the stylus or biro nib installed and it is all too easy to loose the nib you aren't using - as we found found out firsthand!
At least switching nibs is made as easy as pie by the nib-extractor e-Pens has cleverly built into the pen's cap. Merely turn the cap backwards, push it onto the nib and the latter should come away smoothly. The only downside is that with each extraction nibs do get damaged slightly, but then they aren't meant to last forever and are easily replaced.
So what is e-Pens' digital pen actually like to use? For anyone who's worked with styli from various graphics tablets this ambidextrous pen feels much the same, down to the small rocker switch on the bottom section. It's heavier than a normal pen of course, and the e-Pens' broad base extends quite far down, leaving only 3mm of the nib visible. This is usually not an issue, but can lead to problems if you write holding your pen at a pronounced angle.
Range for the device is excellent: the sensor comfortably covers an A4 page, and as long as you don't block it and keep fairly even pressure on the pen it will pick up everything - technically impressive, to say the least. The LCD will always show whether it's receiving a signal by displaying a pen icon.
When you are done writing or drawing in Mobile Mode (i.e. using the combo on battery), simply save your notes or drawings with a press of the function button. The sensor's memory can hold about 50 A4 pages and its LCD will always show how many you've stored so far. Annoyingly, there's no way to not save scribbles once you start (since even if you turn the device off it will still save your most recent pen session), but at least you'll never delete something by accident.