USA Today reports that Apple opened conference for software developers with a preview of its new operating system “Leopard,” which will be released in the spring. The new OS will include enhanced speech-recognition software, a video chat tool, and an automatic backup program. Leopard will be released just after Microsoft releases its long-awaited Vista operating system. Ross Rubin, an analyst at the market research firm NPD Groups says that the new additions “are a strong argument for buying a Mac.” This development, in addition to Apple’s adoption of Intel chips, and the Boot Camp software which allows users to run Windows seems to be fueling Apple’s market resurgence…