I first tried Intaglio as an OS X substitute for MacDraw and ClarisDraw. It can import old graphics files without any problem and has more than enough functionality for my straightforward drawing (after using Intaglio for over a year, I'm still discovering new/useful features). For someone who doesn't need Illustrator or heavy-duty CAD software, it would be hard to find anything better or more cost-effective.

If I could, I'd add an extra star for customer support: I recently contacted Intaglio about a problem with re-installing the software after reformatting my hard drive, and got help within a couple of hours. Pretty good!