I wasn't concerned with the data (obviously all local) but running at 0.5 seconds results in 9 to 10% of the CPU. I am using surf as the browser. I like having the faster refresh while it's downloading, but it's pointless while it's idle.
I'd like to have it refresh every minute while idle, and every 0.5 seconds while downloading. I assume you'd add a config option for both of these times.