I have been using my UR points on its transferring partners - e.g. MR, SQ, BA, and of course UA. These partners also have their own partners, so more possibilities.

Most recently, I transferred some UR points to SPG via MR to top off a week long SPG award stay redemption. On the airline front, I have done a lot of transfers to BA due to good redemption rates for short-haul AA domestic flights. SQ and UA are used for long distance flight redemption, especially when there are good saver awards availability in the *A group (e.g. AC, LH, SQ, UA)