I have been using these for quite some time, and they generally works quite well - easy to write with, make a good clear impression on paper, write over most anything - only downside are the tips tend to wear down after a month or two of use, and occasionally, after plane travel, the ink can leak out the tip - but they are a good value for the money, and are preferable to the other pens (including felt tips) that I've tried.

Good value for money

I think they're a great value, but it would be awesome if they lasted longer, or didn't have the awkward ugly phase that they go through.

Excellent value, fraction of store cost.

good value and will work well with Zentangle.

Good value

They're archival, and I use them in my journals as well as for school and inside of cards