A very good friend of mine and flying partner had a corona and he flew it for a very long time and beat the heck out of it from what I saw it was a good learning heli for him and he enjoyed it quite a lot.I myself did not fly it and so I cannot give first hand experience at it after my friend decided to move up he sold the corona and purchased a JR Voyager E after he saw mine and has been flying it with me for some time now.From what he told me the corona is a very durable heli and can take a beating as for upgrades I cannot say again because I only know what I have been told and have seen from his.I don't know if this helps or not but I just thought that I would pass his experiences on to you.