Tarom tops my list for WORST, banana-republic-without-the-bananas, complete $h!+ airline EVER!!! (in other words, I don't like them). I've been stuck flying them twice and, Lordy....don't even want to waste another keystroke complaining about them...
Kenya Airways is trying to pull up its socks through it's links with KLM, but it is still very much a third-world airline in which customer service means nothing and Nairobi is a nightmare.
I've been on a COPA flight once, and it was definitely up to Continental standards (not great, but not-banana-republic-though-in-a-banana-republic).
Overall, I have to agree with other posters that SkyTeam is really stooping to conquer if it can only attract this rag-tag bunch of airlines. Virgin is too good for SkyTeam, I'm afraid... Every other alliance has a top-notch carrier affiliated with it, but SkyTeam apparently is putting all it's chips on Aeroflot's world-reknown glamour and cachet.