First, thank you to everyone who participated and remember that this is my personal opinion and not an attempt to insult anyone. : )
top 5, from most to least favorite : stippi, 575, kabuto, mc clintock, and zumi
perspective: A 3D perspective is a must. especially since all other GUI elements (scroll bars and borders for example) are 3D. The angled tilt of R5's icons would be very nice to have.
black outlines: For me, it's more of having a double thick border rather than an outline of the color black. 575 uses an appropriate color of double thickness, which blends well with its icon and helps to make it distinct from the background.
shadows: very cool to have, as they can add additional 3D-ness. 2 small conditions to this: the light source needs to be the same as the one that casts the drop shadows on the gui elements, eg coming from the top left corner. the lighting of the icon needs to reflect that light source. one bad example is stippi's trash icon. the top back edges of the trash icon seem to have no width or contact with the light source. also the right-most green edge should have some type of shadow under the grey lip.
true BeOS Icons vs. Heavily Influenced. As much as I love R5's iconset, I would prefer one with a more modern feel. The pulled perspective that Stippi uses adds a very elegant touch to them. ( by pulled persective, i mean how the bottom right corner is slightly elongated in a curvy way ) I like how 575 and Kabuto are still identifiable as BeOS-ish (at least to me) The wrench for preflets is nice too; hints at fine tuning the system.
Honey: the hard drive icon makes the entire set. currently, it's the only set to incorporate some aspect of Haiku's logo into the hard drive / boot drive icon. The only other sets that attempt to use some aspect of Haikus (limited) branding is Alba, Garum, and Kabuto in their application icon.
Stippi: overall, it looks crisp, clean, and probaby smells fresh too. at 16x16 and larger, it looks great. i love how the StyledEdit icon has text only upto the pencil point. the trash icon feels funky to me.
575: overall, it's a playful (but not childish) twist on he traditional R5 icons at 16x16 and larger, it looks great. The CD icon is a nice change, especially as it could be used for mounted image files. It's color specific borders probably help to give the illusion of softer icon colors The Image icon is a bit bland. The use of shadows is inconsistent -- both in location of light source in relation to the other GUI elements, as well as some icons lacking a shadow
Kabuto: at 16x16, most of the icons look at least decent. This is one theme that would benefit from having a double thick border. The hard drive icon feels bland -- possibly because it resembles an image icon (shape and color)
Mc Clintock: Essentially a very slightly modified R5 set. Out of all in this list, I like his trash icon the best, even if it is a bit dark at 16x16
Zumi: The closest set to the original R5's set. Even though Zumi's trash icon is very similar to Stippi's, Zumi's thinner tophalf looks better.