I've been using my standing desk at work & standing while sewing for a 2.5 months now. I thought I'd post a few comments on how it's working out so far.
First, I've noticed that I do many things well while standing. Surprisingly, sewing is easy. Since I stand to iron and cut out fabric, it seems to be natural to just move over to my sewing machine. But I notice for more detailed work, hemming by hand, sewing thread chains, I feel like I concentrate better and longer if I'm sitting down.
It's similar at work. I find I do better with short-term tasks and projects (sorting through email, answering quick questions, reviewing schedules, light research). For longer term/heavier concentration work, I really feel a need to just sit & concentrate. Standing & concentrating just doesn't seem to be that easy.
Another issue is that I only have one way I can put the standing desk in my cubicle (facing south). Which means I am distracted by everyone who comes in either door (I sit by 2 exits). Most people don't speak, just go about their work, but I see them, and that's distracting. Whereas when I'm sitting at my desk (facing west), my back is to whomever comes in either door, and with my headphones on (I get thru lots of podcasts), I can really just focus. I have really noticed the last few weeks that I'm having trouble focusing. (A big deal as I have to do quite a bit of writing & writing is not ever easy for me.)
I can totally see how a geek desk is the perfect solution if you want to stand more. You can set it for 2 levels, and the punch of a button just sends it down or up to one of those pre-sets. However, at $874 for the small one (includes shipping), that won't be happening anytime soon!
If you are interested in making your workspace (sewing or otherwise) more ergonomic, check out this post on Craftsy. They mention chopping off table legs down to fix the height...instead I put cans underneath my cutting table legs to raise the height. (UPDATE: This totally rocks; I do tons of work standing at that table now. Pinning, cutting out, reviewing pattern instructions, much better done standing.)
So tomorrow at work, I'll be using my lunchtime to undo my standing desk & go back to sitting. I think I'll miss the standing, but I'm fortunate in that I get many opportunities to stand and walk in my job. I also walk from the metro, and stand in my kitchen & sewing room. I won't be standing quite as much...but hopefully I'll get some more writing done instead!