These foundation systems are fairly common and have been around for years. There are no inherent problems with them. They work as advertised. The only potential drawback I've run into is - unlike, say, a masonry block wall - they are difficult to repair if physically damaged (an unlikely situation for most) and modifications can be difficult.
Do not be concerned that there is no 'footing'. There is a footing - it's a crushed stone footing, the same as used for wood foundations, and regulated under R403 in the building code. They work just fine, maybe even better because water drains thru them.
Since the materials are only sold to manufacturer-certified contractors, your odds of having installation/workmanship problems are probably less than with a conventional foundation.
Note: I'm a forensic structural engineer and investigate building failures on a daily basis
