I think it's fair to say this is a good community to start out in and get a portfolio going (sort of - i dont consider items, most pets, and most npcs portfolio pieces), get your name out there and make some side cash. However, not a good community for a seasoned veteran of the arts (any kind either illustration or graphic design) simply because of the lack of professionalism. And I think that's partially due to the age group this niche brings in; most clients and artists on here are anywhere between 12 and 22 - too young to really have experience in owning and operating an entire business or purchasing services. Not saying you cant be professional at that age, but the vast majority are not.
I completely agree on the real life vs internet-based clients. You meet them, you know who they are, you have a real, paper contract, and real, legal wages. Also a majority of the time they're representing a company, and most decent human beings will not risk their own job simply to be a trolling pest on your work. They'll treat you as the company would want them to treat you. Weather or not they're nice to you doesnt really matter in my book - if they're a client they're not there to be your friend. It's a completely professional relationship and whether or not they know how to be a friendly social person at least they wont rip you off.