Cubase SX 2.0 is like Photoshop, but for music. It's easy to use, extremely powerful and featureful, and fully capable of professional results for audio recording, processing, MIDI sequencing applications, as well as sheet music.

Something I didn't count on is that a copy-protection dongle takes up a USB port, though I found a neat tiny, unpowered USB hub (and it even passes my Radio Shack $30 Rule*). It's also worth noting that if the dongle breaks or gets lost, you have to buy the whole thing over again, which for the SX edition means $700. (The SL edition is cheaper, with fewer features [PDF]. I went for SX for sheet music authoring, 'cuz, you know, I'm going to be doing a lot of that.)

SX 2.0 is a new major version that was released only a couple of months ago. Mac OS X 10.3 (Panther) is also a new major version that was only released a couple of months ago. The result is bug city. Thankfully, since we Mac users are all running the exact same hardware and the exact same software, we're all encountering the exact same problems, and everything I've seen so far has been mentioned in their support forums with work-arounds. For the Googlers, here's a summary of what I've encountered in my first couple of days:

• That copy protection dongle I mentioned? The drivers that came with SX 2.0 don't work with Mac OS X 10.3. The main symptom is failing during initialization of the Maestro component (even though the "Protection" component succeeds), eventually "unexpectedly quitting" the application. The solution is to download and install new drivers (> 4.3.0.0) from the Syncrosoft website, or from the Steinberg website.
• When opening or creating a new project, it complains about "Samplerate" not being set. Go to the Devices menu, select Devices Setup... Select VST Multitrack from the left sidebar. Click on the dropdown next to ASIO Driver; only one option is usually available, Built-in Audio, and it's selected. Select it again. It will prompt "Do you want to switch the ASIO driver?" Say Switch. You will only have to do this once for all projects, as far as I know.
• When opening an existing project with MIDI tracks created on another computer (I'm guessing this is limited to projects created on computers with Mac OS X 10.2.8 or earlier, I don't know), it complains of Pending Connections about "MIDI System / -963666093," "Not Connected." For each MIDI track in the project, select the track and notice the "in" and "out" (in the main track panel, the one above "Track Parameters") are set to "not selected". Change these to select your MIDI device. If you set up a MIDI-based metronome, this setting will also have forgotten the device: Transport menu, Metronome Setup..., MIDI Output. This will recur every time you disconnect your MIDI interface, which will be common for laptop users like me.
• This one isn't a bug, but worth noting for Cubase newbies like me: If you're playing a project with audio (such as the "Heaven and Hell" demo song) and you're getting pops and crackles during playback, go to the Devices menu and select Device Setup..., then select VST Multitrack from the sidebar, then click the Expert button. Set Audio Priority to Very High. My 1.2GHz PowerBook G4 needed this setting to play "Heaven and Hell" cleanly.
• Sometimes buttons disappear (will fail to redraw). This happens to everybody, and as far as I know, there is no good work-around. Clicking on where a button should be (clicking the button) will cause it to redraw, and saving, closing and re-opening a project will redraw the interface.

Steinberg has already released updates up to Cubase SX 2.0.1.10, which includes the new Syncrosoft drivers, among other things [PDF], though the problems listed above persist. There are more user bug complaints here, though nothing I've confirmed in my so-far light use. The forums are generally useful for a lot of things, it's a very active community, and Steinberg developers and support folk are present.

It's worth pointing out that I had the opportunity to install and run this version of Cubase under OS X 10.2.8 for a week (on another machine), and it had none of these problems (except for the CPU priority thing, which isn't a bug).

* Never buy anything from Radio Shack that costs more than $30.