I use the mems sometimes. Some are quite cool. I learned 利口 this way, for example.
However, right now I'm learning from a topic no one posted mems on yet, so I have to add all these myself. I do so when repeatedly failing a word, or when I can already forsee that a certain word will be problematic.
After 3000 learned, you'll get to know one when you see it :)
In that case, I try to make something embarrassing, shocking or funny - or funny-because-it-aint-funny. __
I always use mems, but I've seen a few comments from people who don't use them at all.
It would be really interesting if memrise could track the learning and retention rates of the different groups, (mem-users, non mem-users, mem-users who don't write their own) and tell us what impact the different strategies have. It might be difficult though to distinguish between the last two groups.
@ikenaiAndi, ah, I see that you have, by chance, just answered the question on mem-use that I asked you on another post! We need to get some more German-speaking Japanese learners onto that topic to help you!
I use some of the mems. As I am mostly using my second language as a base for other languages I get a word I don't understand in either from time to time, even though it is quite rare. I like the mems with pictures or exemples in such case so I don't have to use a dictionary.
Other than that, I don't use them much. But perhaps it is given by a lot of words being just a review in my main languages, I am curious what will change when I really start with a trully foreign and non-european one.