If you were still looking at first class, the Jetblue mint's hard product comes close to many international airlines. it might be worth trying that out. soft product looks a bit the same though.
JB flights look like SW. i just checked JB and i can fly to MCO at 11,200 points. cash value is $129 though so its $.01 per point. I think JB points are easily earned. for example
Amazon purchases are 3 points per $1. although i have not yet received any points from it yet. :\
like what previous said, you lose your ability to earn easily. you will lose your easy status as well. I also dont plan on keeping my personal SPG but i do plan on keeping the business SPG as that has one extra benefit than the personal. as for UR--> Marriott --> SPG, you lose a crapload of value to it. from Marriott to SPG is 1:3 so basically for every 3 UR points = 1 SPG point. its not worth it. id probably stick with Hyatt instead. I believe point purchases are with SPG themselves but you do lose out an on extra 2x points using the Amex SPG.