I'm not a fan of convertible notes as the form of an angel investment.  When I'm making an angel investment, I much prefer to price the round and do a "light Series A" (simple terms, but still a preferred instrument.)  Basil Peters has a series of posts up on Angel blog that talks about the problems of Convertible Notes for Angel Investing, suggests Exchangeable Shares for Angel Investors, and even provides a One Page Term Sheet for Angel Investors.