I'm without both a tablet and photoshop (the joys of doing without my own computer) and I will say that it is absolutely true- if you don't use it, you lose it. Even prior to doing airbrush work I had fallen out of touch with traditional media; hand spasms aside I got bored with it and now I feel I'm paying the price. I seem to have forgotten everything I learned in terms of proportion and shading, so I'm back to square one attempting to hone some terribly rusty techniques and figure out what's fallen out of my brain. For the life of me I cannot remember how to draw hands (properly). Ugh.