I purchased and tried each type of erasable pen offered at JetPens (three
different Frixions, the Uni-ball Fanthom, and this Uni-ball Signo) and the
Uni-ball Signo was far and away the worst of the bunch.
It looks nice and it's convenient to have the eraser on the cap so you don't
have to remove the cap every time you want to erase, and it writes adequately
(-- not great, but adequate), but the erasability was very poor: the eraser only
served to fade the ink rather than erase it, and it was the only erasable pen
wherein the eraser wore down notably as you used it.
The other erasable pens (Frixions, Fanthom) actually are erasable, and I tried
mixing erasers and pens (using the Signo to erase a Fanthom, and using the
Frixion to erase the Signo, etc.), and found both the Signo's eraser and the pen
itself to be very poor at erasing/being erased.
I didn't actually expect this pen to work. I remember the "eraseable" pens from
the late 80s, and how the eraser would wear a hole in the paper before actually
erasing the ink. Hope springs eternal, though, and this time, it was worth the
wait. The pen writes smoothly, the ink is a medium blue, and, though it does not
completely disappear when erased, it certainly erases well enough to fix an
"oops" here or there. I was pleasantly surprised, and will probably order some
more when they're back in stock.