Interesting reads. If you have any help with my Mac issues let me know.
I've now been using a minimac (1.5GHz/1Gb) at work for exactly a year and have made the following observations. A lot are minor niggles, but when choosing an OS that you have to live with rather than tout to friends they become quite significant. I'm a graphic designer and at the peak of my creativity

I have Mail, Photoshop, Illustrator, Indesign, Firefox and iTunes running. I should really have 2Gb at times as I get tedious delays in Photoshop now and again for very little reason. Used with a 20" Cinema screen.
*Things I like*
I suppose I do kind of like the smoothness of the interface
Small form factor of base unit, is tidy
Scaling and tricks of the desktop GUI are cool and useful
I'm sure there's a couple more I take for granted.
Just discovered Itunes/Airport playing - cool!
*Things that I don't like*
Hit boxes on buttons/icons!
I don't want to have to click right in the graphic area of the icon, I want a friendly square for the footprint of the whole thing.
The way the finder works
Can't press "del" to delete a file, have to use the trashcan.
Prefer Windows tree-explorer navigation. Apple's left to right nav is interesting, but after a while gets counter productive- Open request boxes often conceal right edge of file lists.
Identical filetypes sometimes have different icons and associations. Someone know a fix for this?
Having to go to my applications folder to run a program I don't use everyday.
Why can't I cut and paste a file!!?
The OSX environment
Personally I do find it laggy, not much, but just a bit. Buttons performing an action even though they haven't reacted to the mouse etc. When I'm -in the zone- on XP and clicking all over the shop, dragging here, dragging there, I don't feel held back by the interface, OSX seems to just cruise along, looking suave while not actually keeping up. Expose is quick for what it does, no problem with that, but generally not as responsive as wXP to me. Not helped by the fact that I hate the mighty mouse.
I don't like having programs as just large windows/floating palettes. I prefer using a task bar + fullscreen app, I don't like having a program hide at the end of the dock when I closed its window. I feel I only use Expose because of the shortcomings of this way of working, or I just feel like bashing the F9 key.
Spotlight (search tool) is only good because it's fast and well presented. Windows can search inside files too, and doesn't reset your filters when you start a new search.
Applications: just because most programs can run from it's own folder doesn't mean they all do. Adobe software puts things all over the place and even has it's own fonts folder (or at least has two places for those things) causing occasional frustrations. It's 50/50 with the programs that I've installed wether they've had installers (and blue progress bars) or just drag and drop.
Why can't I unarchive a file to a destination of my choice just by clicking/dragging?
The hardware
Quiet little unit is the Mini most of the time, fan gets loud now and again for seemingly no reason in Photoshop. The G5 tower we have here also has a jet turbine inside that turns over now and again. Mistook it for the air conditioning for the first two months.
Have I mentioned I don't like the Mighty Mouse? How could they have that as the leading Apple mouse? Large contact patch = noise + picks up all dirt. Sensor worse at tracking than cheapo mice on sub-perfect surfaces. Thought I'd get used to the "right mouse button" after a few months, I have but it's a hideous way to work.
Plug in play? Mostly maybe, but we needed to install software/ drivers for our printer and our scanner to even appear connected. At least Windows tells you it can see something and has a shot at getting it to work.
But as said before, Garp says it right, each to their own. Well done Hamish (not sarcastic, sincerely) and others, you've found an OS that suits you better that XP. Enjoy it! It sounds like you are

There are always 1001 reasons for and against each platform, most of them are subject to personal preference. Sometimes the OSX environment seems like a better deal with its
togetherness and swishy stuff and easy stuff, but
to me it fails after a year of use because of niggles that I can't fix myself. Plus it made me lose half an hour work time typing this.
