PiquantMenu (more in a separate article) provides nearly all the functions of Filegazer, plus a great deal more besides. It costs a little less, too. Though PiquantMenu provides nice previews of graphic files, its previews of PDF's and text files can't be resized, as you can in Filegazer. For that, though, I found the ideal tool... a little utility called MacGizmo.
MacGizmo, covered in a separate article, lets you preview just about every kind of file you'd want to preview, in a resizable window. It operates as a kind of super-GetInfo, and you use the Finder to navigate. MacGizmo is a little pricey at $20, but it provides the critical functionality Filegazer so correctly points out as missing from the Finder.
One feature Filegazer is missing that might help overcome some of its weaknesses is search. There's no way to search in Filegazer, so right away you lose one of the fastest ways to navigate a large file system. Browsing is fine if you don't know where you're going and have all the time in the world. But if you're a power user who knows where the file is, Filegazer would drive you batty.