I love how easy it makes to load multiple js files in one page without having problems like script conflicts, or that when you change some code there are no errors because your app just stops working! Loading time can be improved but not so much as with other solutions (like CDNs).
The main problem we have solved using requirejs was loading all of our dependencies at once instead waiting for them each separately which made development faster by orders magnitudes due from concurrency issues between various libraries used together.