Personally i wouldn't waste my money.
I find you can do it just as well in Excel, and use something like Sharepoint to control your documents.
I've never seen MyHaccp and have no idea how it works, so i'd be interested to see what others think.
Although managing your documents can easily be done with Excel I doubt you can have your control sheets filled out with it. MyHaccp is not only a management tool but it is also used by my employees to fill out their daily control sheets. It is complete with electronic signatures, dates, time that can not be tampered with. When they fill out their control sheets the information is gathered on our servers, backed up, and give me full access to make file/on site verifications that will be fully documented. The system also uses a form of Outlook Calendar for scheduling control sheets and inspections so unless they are absent they will not miss one.
On a side not it has also eliminated the use of paper control sheets so +1 for trees