Hi.
Thanks for the answers. Keep them rolling in.

I tested the Pilot G2 (ink roller pen) today.
1.) You can make annoying noises with the plastic clip :)
2.) It's cheap enough: I wouldn't like to put an expensive fountain pen in my trouser pocket together with a set of keys. I'm not worried if a G2 gets a scratch.
3.) Nice to handle. Good grip. Easy to use with one hand. Fast action. No taking the top off before writing.
4.) Smearing. I got quite some ink on the outside of the tip after having made some hasty notes. I noticed a few spots on my hand. Would annoy me in the long run.
5.) Good to read: Contrast is much better then with ordinary ball point or pencil.
6.) Possibility of disaster: Anyone ever realized that their Pilot G2 had accidently been pressed in their trouser pocket? Is it easy to clean?

Conclusion:
Nice writing but leaves my hand stained.

Any suggestions are welcome.

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I also like writing with Stabilo Point 88 (fine 0,4) felt tip pens.
(Don't know if they're available outside of Germany. If not: google)
I tend to mess those up rather fast.