I've just started using it, and so far the tool looks interesting. I like its speed, and it highlights real errors (I've tried some checkers before, they also fired useless alerts). Will give it a try for a week or two to decide whether it is worthy of upgrading
Just signed up for Chrome extension, works fast and finds a lot of errors.
Need iOS keyboard, it is missing right now
Installed Chrome extension week ago, works properly on most sites, very convenient in use
usability, stable corrections on websites and social networks
app for mobile would be great update