My Take
Math Pickle is a site aimed at teachers, and is not designed to be navigated by students. Problem solving and fun with math are at the core of this site. Many of the suggested activities, which are well supported with video instruction and necessary ancillary materials, do need direct teacher instruction to be carried out well by students. The activities are clear in their goals, but no attempt is made to align them with CCSS or any other standards. Also, as mentioned above, there isn't really a student-oriented part to this site.
How I Use It
I've used activities at this site to provide problem solving experiences for third and fourth graders. Many of the activities found her rely on collaboration and trial and error with math concepts, and are thus a breath of fresh air to most rote and discrete-skills based math programs. One popular activity called Ballast, for example, is available at three different grade levels (with skills incrementing from addition to multiplication to exponents), and the materials provided in pdf form allow not only task completion, but also task creation, as the open ended nature of some worksheets allows students to create their own puzzles (problems) for others to solve. For teachers looking to build positive and /or playful attitudes toward math, this site is quite beneficial. Just be prepared to invest some time reviewing what is there, since organization of the site isn't optimal, and many activities can only be understood by watching accompanying videos which explain them.