Chase has launched a new transfer bonus: right now, transferring UR points to Marriott comes with a 70% bonus, which means the transfer ratio is boosted to 1 UR = 1.7 Marriott points. This appears to be the highest bonus so far; the previous high was 50%.
UR points are generally valued at 1.5 cpp or more, while Marriott points are only worth about 0.7 cpp, so the math still does not make this an especially great deal. Even with the 70% bonus, the redemption value only comes out to around 1.2 cpp. Still, if you specifically need some Marriott points for a stay-four-get-one-free redemption, this could be worth considering.