And that brings me to the things that this pen was not designed for. This isn't a pen that you'll want to use for long writing stints. It's just too small and uncomfortable. The refill is mediocre and skippy, and there's no other compatible refills to replace it. For me, these are acceptable trade-offs. Remember, this pen was designed for a specific purpose, and it meets that purpose with flying colors.
If you want the flexibility of other refills, the original PicoPen (shorter than the PicoPen Ti) takes standard D1 refills. I haven't tried one, but I imagine it will be even harder to use since it's about an inch shorter! If you're interested, Brad wrote about this one back in 2009.
Overall, the PicoPen Ti is a fantastic keychain pen that I've enjoyed carrying. It's not a long-form writer, but it's a great option for an "always around" option for those situations where you didn't bring the good stuff.
(TEC Accessories provided this product at no charge to The Pen Addict for review purposes.)