I have used CrystalMaker and CrystalDiffract for almost a year now (for inorganic solid state crystal structures). To sum it up - it is very intuitive and it has been stable up to now.


Upsides:
- It is very easy to integrate it with SHELX (e.g. using TextMate scripts) or GSAS (Rietveld refinements), so the overall workflow is much quicker than using WinGX/Diamond on Windows computers, for example.

- The new Spotlight integration is quite useful (although some search tags do not seem to work properly yet), especially if you have got lots of crystal structures on your hard disk.

- The V8.x interface leaves much less clutter on your desktop than the previous version (especially if you are using Leopard's Spaces).

- Renderings for both publications and presentations are magnificent.

- Nice integration of CrystalDiffract (high quality simulation of powder patterns).

- Much more intuitive than Diamond (Windows) for ordinary crystal structures.

- Cambrige Soft has got special concessions for grad/undergraduate students, which makes the price tag quite reasonable.

- Great customer support.


Downsides:
- Lack of visualising magnetic structures.

- Lack of visualising electronic structures / 3-dimensional electron density maps (e.g. from Wien2K or STUTTGART-LMTO)

Hopefully, these missing features will be added sometime in the future.