What do you like best?
very fast database for storing keys and other information into memory that would normally be heavy on other databases / applications to request the data. ability to cluster the memcache servers in a distributed pool for high availability and reliability. integrates with many languages using modules/api (such as c, php, perl, python, etc) allowing greater flexibility for usage.
What do you dislike?
it's meant for specific use cases really. assuming that the server restarts, any of the cached data will be gone (it wasn't meant to save it long term). there's some other products that are supposed to be better as well, although i haven't had a need to try/use any of them yet for the purpose of the applications being used with memcached.
Recommendations to others considering the product
tuning appropriately for your resources available is necessary to get the best performance. it works great for API's, scripts, web applications, etc. it's almost hard to not find a good use for this program, although other one's such as redis may also be useful and one would need to evaluate which one may be the better solution.
What business problems are you solving with the product? What benefits have you realized?
misc_check custom script used with keepalived for the purpose of self adjusting dynamic weights of services (primarily http/s) being load balanced based on the the node system load being checked. it's extremely fast and reliable for the custom check being used and can be integrated for many types of services checked. the daemon itself doesn't really require a large amount of memory, however that would be dependent more so on such data being stored and accessed.