I've found the questions to be too algorithm centric, which does not really represent my day to day. A fresh Uni grad might do well, but as a coder with over 20 years in, the problems are too generic or jargon filled.
Also solving problems IRL allows for google searches, and chatting with co-workers. If I can find an answer on SO that is close to my issue, I save the company money, by not rolling my own.
So. If you're looking for Uni grads, sure. If you're looking for experienced dev's it's a great way to get a pile of "Nah. I'll pass."