A couple things:
First, Apomixis is 100% correct that learning individual characters by themselves, apart from any context, doesn’t work well. Characters I’ve seen often in words are the easiest to learn to write; characters I’ve never seen before and that I don’t have context for are the hardest to remember how to write.
So Skritter on individual characters is an inefficient, boring, and ultimately not that useful way to learn more than 100 or so. I always get huge benefits from seeing the same new material in at least two contexts (for instance, learning it in flash cards, then hearing it in conversation, or vice versa), so you gotta supplement Skritter with something else.
Second, I’ve lived in China for 2+ years and was recognizing ~1,200 before I started Skritter a couple months ago (can write ~1,000 now). Even though I physically have to write something maybe once or twice a year, learning how to write those characters I already “knew” is life changing. I feel way more aware of what’s going on and I’m able to use Chinese apps with an ease I never had before. The investment of one hour for every 30-40 characters is small for such a huge payoff.