Grammar (or more accurately, capitalization) is the difference between helping your Uncle Jack off a horse and helping your uncle jack off a horse. And spelling matters as much or more. The only answer is really not to rely on spellcheck, though. You have to slow down, read more carefully outside the Infinite Elsewhere of the Interwebs, and be willing to edit your posts. The more you've read things written by people who know how to write, the better your sense becomes of what's really execrable. Then you don't need spell check, which is WAY fallible. Or at least you need it less.
For many years Bill Safire had a great column in the New York Times and many of those back issues are still available as compilations so you can feel linguistically inadequate all over again. But I love to read them.
So yeah, it does. It shows you care, and I know it's tougher for some than others.
http://www.amazon.com/On-Language-William-Safire/dp/0380564572
You can also have really positive learning experiences by visiting your local (gasp!) brick-and-mortar Library from time to time. You can spend a few hours reading interesting things the way people have for hundreds of years, in quiet places that are usually run by very pleasant, literate and helpful people. I support my local libraries particularly because I know what kind of uphill battle they face, but not just for that reason. I think more people should give them a second chance.
The Key to Good Spelling, Grammar and Composition is Having an Edit Button and the Will To Use It - Me