Oh, and it's somewhat of a dinosaur. The last version was apparently released in 1994, and there's currently no Debian package for it (perhaps because they figured that everybody should get over it and move on to Electric Eyes or something). Even the page itself looks like a historical relic, with NCSA Mosaic-era HTML, floppy-disk-shaped icons ("daddy, what's that?") and a compress(1)-ed source archives for the people who don't have the new-fangled gzip program. But still, it does the job and does a better job for its humble task than more recent programs.
Mind you, this is coming from someone whose desktop consists of a window manager, an xterm window and xclock. (Yes, I've tried GNOME and KDE; though I found that they just got in the way.)
qiv (http://freshmeat.net/projects/quickimageviewer/) is a good replacement, and its packaged in debian.
I like gqview, but I try to avoid all things Gnome, I wish it was written with the TK toolkit.
I've found Tk to be slow; though that's maybe an artefact of a lot of Tk scripts to be written in Tcl (not one of the more advanced scripting languages).
Personally, I'm fond of Qt, because of the elegant object-oriented API.
Could be in debian nonfreee, as it doesn't really meet the DFSG