beanstalkd is a great project and it certainly inspired some of our thinking. I think of beanstalkd as a more fully functional alternative to simplequeue (what we built/used prior to NSQ - more details in our blog post http://word.bitly.com/post/33232969144/nsq).
Some of the goals of NSQ transcended just replacing our specific daemon that buffered and delivered messages (most importantly the interactions with the lookup service). Because of that, we felt that owning that piece would make it easier to achieve those goals.
Additionally, one of the most important properties of nsqd (the queue component of NSQ) is that data is pushed to the client rather than polled (like in beanstalkd).
Beanstalkd is not stable it has a lot issues even in it current version. If you doing to be sending couple million messages per day beanstalkd is not for you.
Some of the goals of NSQ transcended just replacing our specific daemon that buffered and delivered messages (most importantly the interactions with the lookup service). Because of that, we felt that owning that piece would make it easier to achieve those goals.
Additionally, one of the most important properties of nsqd (the queue component of NSQ) is that data is pushed to the client rather than polled (like in beanstalkd).