One thing I miss in Ubiquity and which breaks the 'command line
experience' as we know it from, for example, the *nix command line
with bash completion and the like, is the ability to cycle through the
possible matches upon repeated pressing the tab key. I mean: If there
are three commands starting with 'foo', say foo1, foo2 and foo3, I
would expect being able to type just 'fo + tab' and have Ubiquity to
suggest the following when pressing repeatedly the tab key:
foo (common part of all matches)
foo1 (first match)
foo2
foo3
foo1 (start over again)
foo2
etc.
I guess it shouldn't be difficult to implement this functionality. It
does not break the current behaviour but extends it and, as I said, it
is consistent with traditional command lines.