My last name is actually simple to pronounce but I usually ask to "just call me Greg", as Grzegorz is probably the epitome of unpronounceable Polish names.
Still, I'm not sure if I'd ever use this tool. Seems somewhat pretentious, even if useful.
If you're Polish and you see a Polish name, you instantly know how to pronounce it. In the US It's more more hit-or-miss due to ethnical diversity and the English language itself.
Come to think of it, I'd like other people to use this site, but still wouldn't use it myself. Maybe it's because so far I can't see a way to mispronounce my last name and I've essentially given up on my first name.
Still, I'm not sure if I'd ever use this tool. Seems somewhat pretentious, even if useful.