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go with the traders that have good reputation, and leave the others. my opinion...

they can co-exist (BTC and XRP)
the ripple network is just great to exchange one coins for another. if we have to pay small fees to use it, well, it's understandable they have to make some profit. I think opencoin keeping 20% of the currency to their use is a bit too much

i already said that in other posts, but I prefer bitstamp because of it's cleaner look and funcionality.
the others, well...have some down parts but are also reasonable

for now, LTC for sure.
after it goes to mtgox, the price will go up, everyone starts mining, and the dificulty will rise (becoming similar to BTC)

of course btc has more popularity in media, so it's price will stay up for some time

I prefer and use bitstamp. It's cleaner, and the SEPA is great