Yes actually I have on many occasions. My friend and "mentor" in a sense works alot with dragons and that's how I came to know more about them and their magick. Very powerful indeed. They have also helped me in many ways, I've been working along side with them for a while now so all I had to do was ask and the results were unquestionable. Don't try to deceive them or control them though, they are very powerful and can see through your intentions.
Dragons are powerful and respectful entities.They will not come to you like a pet if you simply try to summon them. The dragon will only come to you when it feels you are ready. If you want to work with dragons you must consider them your equal first. Just trying to summon it won't make things happen. When the time is right, it will happen.