Just had an e-commerce site go down due to Craft's custom way of handling Sessions. The session directory never gets cleaned up, causing the sessions folder to be littered with tens to hundreds of thousands of orphaned files, causing my server to run out of inodes. PHP has a built in utility to deal with this, but that doesn't work since Craft sets a custom session directory. Looking for a good cron job or other utility that will automatically clean this folder up automatically.
Also, curious if there is work being done on Craft to fix this issue by default. I wonder if the reason it hasn't become as big of an issue as it seems it is (only found a handful of people mentioning it on the Google Plus page), is because Craft hasn't been out long enough for some sites to experience this yet, but they may soon. It took about 4 months for the session directory to get too full on a pretty small hard drive, so I wonder if a number of other sites with bigger hard drives currently have this issue behind the scenes, and haven't experienced any problems yet, but will soon.