Some of these are handy. The onscreen keyboard is more secure than a hardware one (it bypasses possible hardware keyloggers), and could be handy when all you have is a foreign keyboard layout.
However, I find where portable apps generally fall down, is that they are most useful when using a public computer (ie. in a internet cafe or in an office), and these computers tend to be locked down somewhat. Even if you can run the software on you portable storage, you are unlikely to be able to use it to connect to the internet through the firewall.
I think generally, on-line apps (like Googledocs) are more reliable and useful, albeit more restricted and less powerful.