To be honest I think that they work in exactly the same manner as 50/50 and oasis, however because of the nature of beads the surface area should be greater thus improving the effectiveness.
I am now using tubs of gel in conjunction with traditional humidifiers and they work really well. I use the old humidifiers for topping up water reservoires and the gel stops the whole thing over humidifying.
I am now maintainng a nice stable 68% though I still get some temporary (+/- 3%) variations due to temprature changes, but I can see no way of avoiding that until I build a wine cellar or invest in a cigar fridge.