Yes, there are many documented advantages.
Copied from here and then adapted:
...the adjustable keyboard was more comfortable...in comparison with the conventional keyboard.
—Tittiranonda, Rempel, et al. (1999) “Workplace use of an adjustable keyboard: adjustment preferences and effect on wrist posture”
...split keyboards place the wrist closer to a neutral posture in the radial/ulnar plane substantially reduc[ing] one occupational risk factor... ulnar deviation of the wrist.
—Marklin, et al. (1999) “Wrist and forearm posture from typing on split and vertically inclined computer keyboards”
There is increasing evidence that alternative geometry keyboards may prevent or reduce arm pain or disorders, and presumably the mechanism is by reducing awkward arm postures.
—Rempel, Barr, et al. (2007) “The effect of six keyboard designs on wrist and forearm postures”
Alternate keyboard designs can significantly affect tendon travel and may address reduced repetitiveness in typing by reducing the amount of tendon travel.
—Nelson, Treaster, et al. (2000) “Finger motion, wrist motion and tendon travel as a function of keyboard angles”
...[the tested] split keyboard [configurations] are beneficial in promoting a neutral wrist position, which theoretically would decrease exposure to WMSDs such as tenosynovitis in the wrist and carpal tunnel syndrome.
—Marklin, Simoneau (2001) “Effect of setup configurations of split computer keyboards on wrist angle”
...[study results] identified a reduction of symptoms, an improvement in functional status, preference for and increased satisfaction with the [alternative] keyboards, and maintenance of typing speed and accuracy for both groups.
—Ripat, Scatliff, et al. (2006) “The effect of alternate style keyboards on severity of symptoms and functional status of individuals with work related upper extremity disorders”
...[split] keyboards with a slant [open] angle of 10 degrees to 12.5 degrees...are effective in placing the wrist in near neutral ulnar/radial deviation when typing...[and] tilting the keyboard halves 20 to 30 degrees is effective in reducing forearm pronation to approximately 45 degrees.
—Design features of alternative computer keyboards: a review of experimental data.
Analyses of...six studies indicated that the [Adjustable Open-tented keyboard] had a large effect on pronation and ulnar deviation...
—The effect of three alternative keyboard designs on forearm pronation, wrist extension, and ulnar deviation: a meta-analysis
Note that there are also advantages in using a soft-touch keyboard and a keyboard without a keypad.
