As you probably know, Q/K are in the lineage of APL languages, with strong inherent vector-oriented capabilities, but Q uses an SQL-like dialect of words to replace APL's symbols.
I've always found the idea of APL exciting, but it seemed to be a very isolated platform. "How do I use this on my site?"
Q speaks SQL natively (using s.k) so it's easy to work into my MySQL-based flow, though not exactly the same as MySQL's syntax.
It's got great built in facilities for bulk data loading and storing, which saves you a lot of time with the boring "getting my data set up" step when banging out little helper scripts.
I've begun using Q as a cache in place of memcache/redis because I much prefer being able to ask flexible questions with a dynamic query language. Example: A MySQL query on a 1m row table that was often showing up in my slow query log at 1sec+ took less than 50ms in Q.
Obviously Q and MySQL are apples to oranges, but it is still a handy adjunct when you need serious speed without full loss of flexibility.
And writing Q directly is a really interesting exercise. My PHP and Node code has gotten better as a result.