I'm only silver level these days.. don't fly near as much as I used to.
But all the status and miles do/will transfer to Delta just fine. The only downside, is if you're a lower-level elite - you're fighting with a *much* larger pool of status members for upgrades and such on many routes.
I still generally get upgraded MSP->ORD, but have noticed a drastic reduction in the upgrades in the reverse - which makes sense, as Delta should be routing more folks through to MSP to hit International (and west coast) connections.
Really for the higher-level frequent fliers, the merger was great. Way more options to use your status - especially internationally. You do NOT want to be in coach on flights to Asia
But, for MSP based fliers - I really think it's going to very likely suck balls. I don't think many really realized how lucky we were to live near one of the countries larger hubs (in terms of destinations). Everything was one connection away at most, vs. the standard 2-3 for most "spoke" airports.