Review unit provided by Kobo.
Included in the box is a replacement pen nib, nib remover and one AAAA battery.
The body is metal and has solid build quality. It's slightly heavier than typical pens and is comfortable to hold. The body is cylindrical so be careful not to let it roll onto the floor.
The Kobo Sage PowerCover has a slot to store the pen.
The side button closer to the pen tip is the highlighter and the next one's the eraser.
The Microsoft Surface Pen is actually also compatible with Kobo Sage and Kobo Elipsa. However, the Surface Pen is more expensive.
Writing experience is different with Kobo Stylus and the Microsoft Surface Pen though. The Surface Pen has a rubberised tip so there's more resistance when writing. Kobo Stylus pen nib is plastic throughout and smoother while writing. When writing, you want to write fast so the Kobo Stylus is probably the better choise
Writing performance is good. No pairing is necessary to use the pen. Battery life for such pens with removable batteries is usually several months long.
The pen supports pressure sensitivity. With the included note taking app, there are options for different pens, e.g. ballpoint, fountain, calligraphy, and different shades of gray to choose.
Erasing will remove the strokes rather than the pixels. The software will gray out the erased strokes, wait for you to erase everything before refreshing the eInk canvas to remove the ghosting lines.
When using the highlighter, you can layer strokes to make them darker. There's no white ink though, so you can't have a black area and write white text.
You can also mark up eBooks you read.
Note that the mark up or text will be saved automatically. The mark up will only be visible at the same font size you used when you created the mark up.
If you change the font size after you mark up, the mark up will disappear into a small icon on the right side. When you click the small icon, the original mark up and font size will be shown in a pop out box. It's best not to change your font size after you mark up so to avoid the extra step of having to click the icon to reveal your mark up.
Delete line mark up is easy as you just have to erase the stroke. To delete highlighted strokes, you have to un-highlight the stroke and it's not easy to un-highlight to the precise letter.
All your mark up will be stored under annotations. Unfortunately, there's no way to delete the mark ups from the annotations page. You have to go to the mark up to delete it manually. It's not easy to remove highlighted strokes.
You can mark up PDFs too.
Mark ups on PDFs will scale together with the page and won't disappear like eBook mark ups.
This is a good pen and accessory that performs well on the Kobo Sage and Kobo Elipsa for writing and marking up.
The only thing that needs to improve would be to have more note taking functionality with the included note taking app. And make it easier to erase highlighted strokes from eBooks.
You can find the Kobo Stylus on Amazon.com or from Kobo's website. The price of US $39 or SGD 59 is reasonable. At least it's noticeable cheaper than the Microsoft Surface Pen.