yep you're right. The only drawback is the time taken for your options to convert to heads. During the conversion the SP could go down for example - and you wouldn't be able to sell either the head shares or the options you are trading them for. A small risk in my opinion.
Also, if you thought the SP was going to continue to rise you could argue that you're better off to use the 2.5c conversion money to just buy more options.