Very comprehensive comparison of various modes of communications. It looks like Google Wave scores on almost all aspects. But still i hasn't picked up as expected.
If this is the case, then can we at least conclude that Wave has come ahead of its time and it is just people are not used to this new concept. Let us wait and watch how Google will take Wave to the next step.

Update 12-Aug-2010: Given that google had taken down / stopped any further support on Wave, it does confirms my belief that it has come ahead of its time. RIP