Yes! Definitely use a safety harness, and the after market ones are much more comfy than the ones that come with the stands. I generally like stands with somewhat of a large platform, it feels good to be able to move around a little bit when pulling an all-dayer.
Also, you would not believe the difference a foot rest makes while in a treestand. Trust me on this one. You can also buy after market seat cushions that strap down to the treestand's seat. There are some good ones out there. I've also heard of some guys taking the cushions off of the patio furniture and using them since they don't soak up water. Hope some of these tips help you out.