XMR is currently challenging DRK. I think if the GUI wallet issue gets sorted out it might be able to challenge LTC even. Cryptonote coins are here to stay (well, except MountCoin, HorizonCoin, OrionCoin, duh. you can't fix an incompetent dev...)
Thank you.
I don't know about the GUI wallet issue, I use the official command line one, but there is indeed a need of VERY good CN wallets soon, the exchanges need that.