Well there is a reciprocality in benefits in Europe on AF/KL - you get lounge access, extra baggage allowance and preboarding.
The main benefit of being an elite member in Europe is the access to lounges, upgrades are not included as the aircraft have adjustible curtains to tailor to the demand.
There's also quite a strong rumor/feeling that Skymiles will not operate in Europe next year and all European members will be integrated into Flying Blue (like the current WP-FB agreement) and that all North American Flying Blue members will become Skymiles members.
This should not surprise anyone -- we'd have DL only doing what DL wants to do .... yet again.