To give a quick overview I took some shots of my own gallery, though it doesn't quite look as awful as it is since these are shrunken:
Neat and Tidy
HUGE thumbnails making you see less art at once
Zero breathing room between each thumbnail
Organized grid all gone
Ugly white rim for "odd" picture sizes
Near unreadable Folder and Comment text under titles
I guess the left align text is kinda nice though....?
Most of all it will make all your art blur together and give a cluttered unprofessional look, it also takes longer to get a good overview if you're skimming for something in particular....
[Ponytunes] last updated 06/01
[pixeljoint] pixelart only
[craftems] flickr for handycrafts