This loop is really fun. If you visit at any time other than the summer, be sure to wear orange because the state of RI allows hunting 7 days per week and park rangers can fine you for not wearing 200 square inches of solid blaze orange (no, orange mesh is not allowed).
This was my first time running the loop. Though, previously I cross-country skied part of it and rode my mountain bike on the sections that coincide with the north south trail. Many sections are rocky and technical, which is pretty typical of trails in the Northeast. What RI lacks in elevation gain, it makes up for with rocks and roots. I ran it clockwise. It is well-marked except for when it hooks up with access roads. I recommend bringing a map or device that can help you navigate.