I flew IAD-DEL via CDG on AF. It worked out well (granted, I was in business class). You're right -- you don't get much from being merely SkyTeam Elite. The most valuable benefit may be the redeemable mileage bonus. Additionally, dedicated check-in (featuring a much shorter line) in the chaos that is DEL on the return will be nice.

Only you can assess how much you value the miles compared to cash, but $100 for 16,000 miles or so (not including bonus) should be well worth it; that's two-thirds of the mileage needed to redeem for a domestic round-trip flight right there. Plus an 8,000 start in EQM for 2009 before the end of January 1!

I haven't flown BA long-haul, but I would imagine that the experience would be a bit nicer than KL or AF. I don't know about CO, but I would personally rather break the trip up in Europe than sit straight from EWR-DEL in economy. But that's just my own preference. Others probably have the opposite preference.

I share your concern about a connection involving airlines that are not partners. There's always a risk. I wouldn't want to have to count on, for example, AI's customer service at LHR.

For SU, you might want to check whether you would need a visa to transit SVO. I would assume that that experience would be pretty grim (the airport certainly is).