I don't know about the good part but I'm dead certain of just one bad part that would make any sane person stay away from these quasi-monies. Such coins are centralized which means there is a single entity behind them. It is not a big deal and a lot of pain in the ass for a government to forcefully close or shut down such an entity. That would mean instant death of the coin. Simply put, governments don't like private money in general. There were efforts in the past (even before Bitcoin) to issue such money, which aimed at creating a universal means of payment and exchange, as opposed to promissory notes and bills of exchange which are also forms of private money, though not universal. Needless to say, all such efforts failed as governments were quick to nip in the bud and halt any such activity. They will never willingly give up their monopoly on creating money or tolerate competition in this field.
Governments are putting up with cryptocurrencies because they can't effectively fight with them. This is evidently not the case with centralized or private money like Ripple or whatever. So there is no reason to think that such currencies will ever be able to take over cryptocurrencies like Bitcoin and friends. As soon as they get traction, they will be destroyed.