As someone who stays at Marriott's often and has been credited for 182 nights this year with more than a million points, I was excited to hear about the merger. Once I got down to planning my last redemption of points, I looked into both SPG properties and Marriott properties. Converting my points to SPG was going to get me a crappy Sheraton for more pts than just staying at a Marriott resort (cat 8). The value of the SPG points was shockingly low.
This is anecdotal evidence of course but transferring Marriott points to SPG has been a loser anytime I've planned. In saying that, some of SPG's higher end properties look just amazing. Now, f you had a bunch of SPG points and moved them to Marriott you may be able to make out like a king!