It's easy to let your your Drupal core slip behind a point release or two if your workflow doesn't support making quick, painless code replacements. I update core using a patch, which allows me to retain customisations I've made to robots.txt, .htaccess or anything else without messy and dangerous file shuffling.

I use a Macbook Air as my main Drupal development machine these days. Although this laptop is perfectly capable of running MySQL, Apache and PHP on OSX, I keep all that inside an Ubuntu Linux virtual machine, and use some tricks to maintain the dev server's filesystem directly with OSX applications like Text Wrangler and Finder. It can be surprisingly time-consuming to set up, if you have no idea what you are doing.