I don't have my own photo, so I took the liberty of borrowing this nice CC-licensed one. (source)
The 78G might be the flashiest of the low-end pens; it looks like a cheap pen pretending to be expensive. Whether it succeeds is debatable. I can't say I like the pseudo-bling look, and I wish Pilot had spared us the tacky gold plating. But it could be worse; I've seen some expensive pens that look worse. (It doesn't look half bad in the photo above, but that's not representative of real life.)
It comes in four colors, and includes a big round sticker saying "PILOT -F-", as if you might forget the nib size, which is also marked on the nib itself.
Seems pretty solid. I've been carrying it around a lot, and dropping it, and I think it will last. It has a screw cap, which might be more secure than a snap-on cap.
Weight & Dimensions
Very light, which is probably good. It's very short without the cap (4 3/4" including nib), but with the cap the length is OK (5 7/8"). The worst thing about this pen is its thickness: the grip section is the thinnest part of this already-skinny pen (about 3/8" at the thinnest point), and I find it uncomfortable to hold when writing for long periods, especially because it's also a bit slippery.
I wanted a "fine" nib that was really FINE, comparable to an 0.5 mm rollerball or smaller. The 78G's nib is exactly that; it's great for subscripts/superscripts and detailed drawing. The thickness also varies noticeably with pressure, for those who like that kind of thing.
Now for the bad news. When I first got it, the nib was so scratchy that it was barely usable, and the ink flow was terrible--part of the reason it had such a fine line. I gave up on it for a while, but figuring I had nothing to lose, I tried a couple of tricks that I read about here. First, I tried writing on a rough paper bag--I wasn't sure that would work, but after a while it really did seem to help. Second, I used a razor blade to cut along the groove in the feed, hoping to widen the channel for the ink. The 78G is easy to take apart, so this was easier than I thought, and it also seemed to help: when I was done, the pen was usable, though still not very smooth and a bit less fine than it was before.
The pen comes with a converter, which is nice; I'm glad that Pilot expects people to use bottled ink. The filling mechanism is a thin rubber tube surrounded on two sides by a metal frame, which you squeeze while immersing the nib in ink. Unfortunately, it takes many squeezes to get a complete fill, which is not even very much--the constant refilling gets old after a while.
This is cheap for what you get, especially since it includes a converter, an essential that doesn't come with other cartridge pens. I'd say it's a decent value, though not an amazing value as some would have you believe.
I'd recommend this pen to anyone who wants a really FINE line--that's probably the #1 reason to get one of these. But I'm not sure there are any other good reasons. It's not great for long writing sessions, due to its small ink capacity and uncomfortable size.
Edited by the oxford comma, 19 December 2011 - 04:09.