So, I installed my Varidesk on January 20. That means I've been standing for part of each work day for 2.5 months.
I am still glad I have it. I like taking my shoes off and standing on the gel pad, and moving around as I stand. I know I feel better for having it. I'll confess that there are days when I am tired or out of sorts that I think, "c'mon, I don't WANT to stand up." But I almost always do it. I'm standing 30 minutes of each hour now.
I was starting to have some foot discomfort immediately after getting out of bed, and I notice that's subsided. Mostly, I appreciate not working in a chair for a solid hour or more, then standing up to go to the restroom and feeling like I'm going to fall down.
Here's a good article with more reasons that it's a great idea and ways to maximize the benefits.