As others have stated, cloud "IDEs" are a long ways off from matching features found on their desktop counterparts. I currently favor RubyMine in my development, which is so powerful its only downside is missing its features when having to use anything else.
I remember the days of Visual Basic 6, and I don't think there's any cloud IDE today that could even match that old relic, let alone modern IDEs..
That said, a cloud IDE is very compelling to me (see my downside on RubyMine), so I can't wait for browsers to be powerful enough to offer something akin.