I am one of those who prefer desktop interface consistency rather than having every couple of applications with different interface looks, depending on the gui framework they are built upon. Variety is the spice of life, but not on a computer desktop, please.
Mac OS X has always 'suffered' from this diversity of gui presentations, like the rest of Unix variants, and Tiger is even worse. We have some metal apps (Finder, Safari, ...) some Aqua (Mail 2) and some hybrids (iTunes 6), not to mention the java apps like Zend Studio, and so on. But in my opinion at least the Apple applications should have absolute interface consistency, being the design wizards they are.
Third parties have provided solutions to this problem for a few years, the most famous Unsanity and its Shapeshifter product. I used it during the Panther days, and I installed a shapeshifter theme that turned every app into the metal interface. Pretty solid and consistent, I liked it a lot and used it for months, the only gripe being that my desktop turned maybe too much grayish. When I upgraded to Tiger I was happy with the novelty of the new gui tweaks here and there, and so I didn't want to install my shapeshifter metal theme anymore. Also, shapeshifter themes tend to change way too much things in my opinion, I just want a consistent gui that also recalls being Mac OS X :-)
Enter the freeware software UNO from Pedro Grilo:
UNO derives from the Latin word for one and stands for 'as one'. UNO is the root of Unity.
UNO is a theme that brings the sunken unified toolbar/titlebar look&feel to every single window on your system cocoa or carbon, metal or aqua and already unified windows as well). On an higher level, UNO's main goal is to enhance aqua interface consistence, by making all elements look&feel 'as one'.
And it does exactly what it says! In other words: Finder, Safari, iTunes and the rest of the cocoa apps all look the same now! This is gui consistency heaven now, thanks Pedro :-)