The solid value of Membership Rewards (MR) points comes from the owner’s ability to transfer them into airline and hotel programs, often at very favorable ratios. MR points can also be redeemed for gift cards and shopping purposes, but that would be a definitive misuse of MR points.
Redemption: The most notable transfer partners include Air Canada, British Airways, Delta, Hawaiian, JetBlue, Frontier, and Hilton. The best value, by far, is when American Express runs a promotion giving a bonus on MR point transfers. These bonuses have historically ranged from 20% to 50%, most recently with British Airways and Delta, which can be awesome. The fact that MR points are not transferrable to United, US Airways, or American is a huge detriment to their value.
Louisa signed up for a 75,000 American Express Gold card in 2012 and took advantage of a 50% transfer promo to British Airways, so she ended up with 112,500 BA Avios points from one card!