I have had a standing desk for almost 6 months now and I couldn't be happier. I have lower back herniated discs and sitting exerts way more pressure on my lower spine than standing. The added benefit is that I get to move and stretch more easily then I'd do sitting.

I do not stand the entire day though. I take short breaks by sitting on a high chair. I stand for about 2 hours and then sit for 15-30 minutes. This has worked way better than any ergonomic chair for me.