I've stood in a wooden 'Oswestry standing frame' nearly every day for the last 14 yrs. Usually 10-25 minutes.
Any benefits? Hard to tell, I guess the next step is to
not stand in one everyday for the next 14 years and compare the differance!

They say it's good for keeping bone strength and density,
(I can't personaly prove this).It's a nice feeling to be up on your feet and gives all the leg muscles a good stretch.
Good for the bowels & digestion too 'they say' as gravity can work it's magic
(although not up in the frame obviously, unless you're unlucky or taken too much figjuice!) I have more often than not had little problems over the years in this dept.
(touch wood, that wood be the wooden Oswestry standing frame of course!)I have mine set up so I can move it in front of my desk and then put the keyboard of my PC on the shelf in front and do a little surfing on the web to pass the time.
I'm c6/7 but I can lift my self up into it but I do need assistance to 'strap me in' so to speak.
If you have the time and assistance, I'd recommend using one, there are even frames out there where no assistance is required.
Get yourself checked out or ok'd by a physio, Dr or O.T. first if you haven't done anything like this for a while.
Good luck!