This used to be my go-to white pen of choice (before I discovered Uni-Ball's white pens). It has a nice consistent line and on plain paper it works very well; for most people who will only be using it to write on dark paper, they're excellent pens.

However, for what I use white pens for (drawing highlights overtop of marker colored drawings), often it would soak up the pigment from the marker underneath and turn a light shade of that color, rather than a flat white. If that's a look that you want (a lightly colored mark to match the color under it, instead of just flat bold white), than these work very well. However, if you want your white pen to be WHITE, no matter what, I'd try a different pen.

Simple...Best white ink pen I have used.
I use copics and adding highlights to my character's eyes are a lot easier with this. The ink is nice and very white. The price is great. But it's not meant to do a large area. Small to medium areas.
Overall, recommend this.

Really great pen! It does as well as the Uni-Ball Signo Broad in white but good for spot work and half the cost.

This pen works twice as well as Pentel Sunburst Gel in white and Pentel Hybrid Gel pens but again, not nearly as costly. I've two and am glad of the investment.

http://fc01.deviantart.net/fs71/f/2011/364/7/c/white_ink_tests_by_colanah-d4kqd qu.png

I draw quite a bit, so having a good white pen for 'shines' is important to me. The Gelly Roll works pretty well, probably the best pen I've found so far (not that it's had much competition). The ink is thin enough that it's not too cakey, but thick enough that one good layer of it does the job. The only big problem I've really had is that the ink I use on my drawings is NOT compatible with this at all (the ink is not water-proof, but is alcohol marker proof). Thank God I tested it before using it on a real drawing, the pen swirls about the ink as if it were dipped in black. If used with other Sakura pens though, it works like a charm. Overall, good pen.

I actually bought this at a local art store near my apartment, but I want to write a review to help fellow artists.
This gel pen is great! Please buy this! This pen dries quickly after applying it onto your paper. And it's great for making highlights and corrections.