written for .NET, not ported from a different architecture (so uses the framework's features better)
configuration is stored in app/web.config (sample configuration file is included) or can be done from code
uses minimal locking to increase the throughput
supports consistent hashing for keys: a specific item goes to a specific server every time. (based on libketama, http://lists.danga.com/pipermail/memcached/2007-April/003834.html)
operations are factored into separate classes, so they are more separated from the main client class, easier manageability and thread safety
primitive types (currently some numeric types, bool, DateTime, byte[] and strings, but can be extended) are stored in an optimized form; only Objects are serialized
excessive extensibility: define your own configuration, serialization format or "consistent hashing" algorithm (see Cannot resolve release macro, invalid id.)
based on our non-disclosed specially handcrafted in-house performance test we're the fastest C# client ever, using negative amount of system resources, be it memory or CPU time
we follow memcached's protocol specification as strictly as no one else: even the memcached guys ask us if they don't understand something