They're helpful in providing samples of their work for me to choose from when I'm considering what kind or style would be best suited towards my needs as an illustrator/designer! The pricing can sometimes seem high at first; however it's not that bad once you've used them enough times so they become more affordable (and worth every dollar).
If there is anything about these services which isn't great - perhaps just because this particular service has only been around since 2012-2013 but maybe things have changed now with some other companies out competing? It was also difficult finding someone who could help guide us through our project we were working together upon during those years while waiting until one became available within your own team members' schedules etc., though ultimately everything worked itself into place eventually :) Thanks again guys!! Just wanted people like myself looking back over.