I'm not quite sure what you mean by seamless. But the Lightroom program is virtually the same. It's just a difference in licensing. You would uninstall the standalone version, and then install Lightroom through the creative cloud manager (whatever it is called). That installation from the CC would simply open the same catalog and you would proceed normally. However, if you purchase Lightroom 5 and then when you join the CC program Lightroom 6 has been released, after you install Lightroom would have to create a new copy of your catalog that conformed to the new format. My experience has always been that that conversion has been seamless as well. Just be aware that regardless of how long you have had Lightroom 5 you will immediately start paying the monthly fee when you join CC.