One thing I dislike greatly, is the lack of any sort of verification. I've already had a number of catfishers trying to waste my time, in just a month using OkCupidDating . Even Kik groups are able to verify people without people having to give up their anonymity, by asking for a live pic to be sent, doing something random that the owner/moderator asked for.
Also, on the web version, if you are typing an initial message to someone, if you hit return, it immediately sends the message, and you have no way of going back and editing/continuing your message, which means you might lose out on a very good match, because of a nonsensical first message.
Many questions are lacking a good choice, I.e there is a "yes, love it", "no, hate it", but nothing in between, so the % match numbers don't really reflect how compatible people really are (something that can often be seen when reading the detailed explanations)
On the positive side, I love the wide range of questions, the ability to add detailed explanations, and all the different categories to handle non-binary gender ids, and being able to find people looking for non-monogamous or polyamorous relationships.