Six tiny words that adequately defines my opinion of Google Wave: "too many features with no direction".
When I was first invited to play with Google Wave, I was all excited about it but immediately became overwhelmed with the sheer amount of features it had. It had features like my instant messenger. It had features like my email. It had features like a PowerPoint presentation. The problem? I needed to relearn everything. Again.
Then came the question of who the software was built for. Who were the target demographics? Who benefits from using this software? These things are relevent because the majority of people aren't creative enough to figure out how their lives can be enhanced by these tools.
To this day, I've yet to figure out the full benefits of Google Wave. Perhaps I will play with it again some time, but by then, it probably won't be around.