I remember the day I saw my first sweet heart latte art in a cup, I didn't know if I should drink it. I'm now going into this business and I love it. I to am still learning to make that great latte art sweet heart. I just started working for Coffee Bean and Tea Leaf I'll sneak a latte art when ever I can... one thing I started doing and let me know what you think of this... I ask the customer if they want a sweeter in their espresso, then I'll add the milk... how does that sound to everyone.
latte art is really for the barista. the customer that notices or cares is relatively rare. i think it is fun & interesting in and of itself.
I feel your pain! The best rosetta I ever did was on a non-fat latte, (go figure) and just as I finished it off, the customer goes "Oh, no foam on mine." I literally had to take a spoon and scrape off my beautiful art, my achievement that took so many hours of work and practice, and dump it into the sink. It was painful, but I've made better art since then. Plus I have a really good horror story to share ;)