I took the plunge and bought a 20" Intel iMac right after Jobs announced it. It showed up around 1/17. Here's my impressions so far.

The keyboard sucks. There's virtually no feedback from the keys and I frequently ended up with double characters. I swapped in the keyboard from my old B/W G3. It's better, but it's not full sized. I'm waiting for the new one from Logitech for Mac users and see what reviews have to say.

Mighty mouse is a non-starter for a 3-button guy, although the scrolling ball on top is very smooth. I ended using a Logitech MX1000 and installing USB Overdrive. It works great.

Safari is ok, but it lacks one very important feature: The ability to save your browser state when you close the app (like sessionsaver for Firefox). Firefox and Camino, the two big-name alternative do not seem to make use of True Type fonts, which makes them look rather amateurish.

As a linux user, I encountered the following issues:

The underlying filesystem is not case-sensitive. This is a little unsettling at first, like when I tried to create a symlink from ~/Mail to ~/mail in my homedir. Yes, you can change to a case-sensitve filesystem, but it requires reformatting the drive and reinatlling everything and some applications may not work properly.

Mail.App doesn't support a local mail spool. Yes, you can trick it and pop/imap from localhost, but it's a poor workaround. I'm a mutt user on my linux machine and have my mail filtered and delivered to seveal folders before reading it (keeping mailing lists out of my primary mbox). Mail.App doesn't support this very well. To its defense, neither does Thunderbird. So I compiled and instaled mutt. I'm happy.

Useable font choices for terminal windows are limited. I ended up using Lucida Sans Typwriter Bold 14 which is a good compromise between legibility and screen real estate.

The system only recognized the first 128Gb of my 250Gb firewire drive. I'm told this may be a limitation of the internals on the external drive. I plan on trying a USB case to see if that fixes it.

Startup scripts are in weird locations and use XML files for their configurations. Evidently, somebody thought there was a good reason for this, though I've yet to discover it.

All in all, I was able to turn off the linux box after about 2 weeks of hacking the Mac. Beyond mutt, I ended up installing aspell, clamav, BerkeleyDB, DCC, razor2, spamassassin, and subversion (I do open source development work in my copious free time). I still need an ascii html browser. links won't build. I'll give lynx a shot next time I need one.

As a Windows user, I have not been able to make the change 100%.

I'm a heavy Quicken user. There is a version for the Mac, but it missing several features and has a completely non-intuitive interface (i.e., non-Mac and non-Windows). It actually reminds me of Mac apps written in the early 90s. I've also tried GnuCash and Moneydance. If you haven't, don't bother. They won't come close to Quicken for Windows either.

Adobe is holding off on offerring Univeral Binary apps until theie next releases. I guess I'll be photoshopping on my Windows machine for a while longer.

While there are many dvd rippers and burners for OS X, I have yet to find one that comes close to DVDDecrypter and DVD Shrink in fucntionality and coimpleteness. I've tried all the commonly known ones for the Mac, including, mactheripper, dvd2onex, dvdbackup, handbrake, and ffmpegx. All have shortcomings.

OK, that's all for the negatives.

On the bright side, the display is fantastic.
The machine is quiet as a mouse.
All the power of FreeBSD wth a better UI than anything from the *NIX world.
It's fast with Universal Binaries and fast enough for those that need Rosetta(note, I'm not trying to use Photoshop though).
It looks incredibly cool (but you knew that).

So, I guess I'm waiting for some virtualization software that will let me run my Windows apps (Virtual PC does not work for the Intel iMac).

If you're a linux user, you can move over without much fuss at all.

If you're a current Mac user who's looking to upgrade, my advice would be to wait until thee are more apps that use Universal Binary.

For Windows users, make sure everything will be available on the Mac (see my caveat about Quicken when assuming if there's a Mac version, it's just as good).