Earlier today the BlueMix UI was updated with a number of improvements. The general theme of this set of updates is to help you find the information you need, when you need it: Search enablement in the catalog and dashboard, ability to mark your favorite applications or services, “Quick Docs" functionality to gain fast access to the VCAP_SERVICES information for services you've bound to an application, and improvements to service creation like assigning a meaningful name to the new service instance.
While most of your applications should work just fine in the cloud, remember: Don't write to disk. The file system is a resource that isn't persisted. As you application instance gets restarted, updated, scaled or recreated, the file system it sits on changes. Using the disk for temporary or cache purposes is OK, if you need persistent storage, create a database.
BlueMix includes a general purpose caching service powered by WebSphere eXreme Scale to really accelerate your applications in the cloud. You can use this cache to store user profiles, store frequently accessed data, or as a general purpose state store for your application. There are two primary APIs to the Cache: Java and HTTP REST. You can learn more about these APIs in the WebSphere eXtreme Scale InfoCenter.