Apple develops its own machines and software, so you get superb compatibility with Macintosh hardware, where Vista has been known to have several issues with many different branded computers. In many cases, Vista "just doesn't work", and Macs tend to. Macs have been known for their usability. It depends on the individual user, but that's how it is for many people.
If you don't like the default backgrounds in OS X, that's fine. Use your own. For things like that, it is your opinion that matters.
Built-in applications like Time Machine come in handy as well as the iLife suite, all of which come pre-installed on brand new Macs. Many Windows computers do not offer the same package. Then there is security... Now I'm not saying that OS X is better because there are no viruses in the wild for the system, but rather Vista has some good security features, save one problem: usability. I've heard people say that they can't ever figure out how to use some features in Vista, and if they can't use simple features that come with it, then they can't take advantage of its higher-end security features either. I'm not a Vista user, but I have used it on other people's machines. It's definitely different.
If you were running CS3 on both systems on the same MacBook, then I'm not surprised. Have you seen this? Different systems, but same hardware may be the case, so long as performance was relatively similar. Plus the MBP can run Windows very, very well. While they've already tested that there are faster Windows notebooks out there, that's impressive. Apple's high-end notebook, which does not even come with Windows installed nor requires that you use it, can best several other Vista machines. Not bad at all. OS X applications also share numerous files together, particularly Apple's programs. iLife, Final Cut I'm sure, and their other suites, can all access files from iTunes or the Media Browser, or wherever the media files are. The integration is great.
When it comes down to it, the user really affects how "great" an operating system is. OS X is great for multimedia and design, etc., but it's also great for everything else. Gaming is another matter, but I've played a few games on my MBP, and when I turn the graphics on high, the graphics quality is amazing.
-BMF
I just bought my first apple computer, a 15" Macbook Pro, and I like it. For $2200 dollars (student pricing agreement) I got a dual core processor, 4 GB of RAM, a nice graphics card, and its a good looking computer. I couldn't find another company offering this kind of hardware for so cheap. However, I don't see why people are always boasting that OS X is so much better than Windows. I remember reading in a forum awhile back about how much better OS X's desktop looked and functioned compared to Vista. This I strongly disagree with. I personally don't care for Vista's little side bar with useless information (I always deactivate it to save memory) but the aero interface that allows you to quickly flip through differnt windows using a mouse thumbscroll wheel is far more efficient and visually pleasing than the OS X alternative. Sticking with desktop appearance, I think Vista Ultimates video desktop background is very cool, granted you have to have RAM out the wazoo to run it and not effect the overall system speed. I also don't see any difference in terms of overall performance. I installed Photoshop cs3 on the mac and vista partitions of my laptop and loaded up the same, extremely large file for both of them. No difference in performance at all. So my question is this, whats so great about OS X? I'm not bashing it. Rather, I'm hoping somebody will point out aspects of OS X that I may not know about. Right now the one thing that stands out about Apples highly touted OS is Boot Camp. Atleast they have the common sense to know that people's computing needs can't always be met with one operating system. I wish PC's had this same capability.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic