Software: Autograph for Mac OSX

After a stressful but educational upgrade experience for Snow Leopard on my Apple powerbook, I needed solace in some new software - something fun, useful and cool, the sort of thing I could use on my morning train and draw gasps of amazement from my fellow travellers. I couldn't find anything quite like that, but I did find Autograph from Ten One Design. There is a free version, which has a watermark, and a paid version (which doesn't) and costs about 7 of those 'greenbacks'. The watermarked one is pretty useless to be honest; however, the licensed version is really very good, and will now avoid the panic and cuss words that follow me finding I need to physically sign an electronic document. Oh, it needs Snow Leopard and a modern (black keyed) macbook pro with a trackpad.....