I spent some more time on Reaction Grid yesterday. Although it has a way to go before offering the features and stability of Second Life, it's easy to see that it's just a matter of time before OpenSim grids will be viable alternatives.
I shot some HD video that I'll edit and post here later this week. For now, here's a very short clip of being on Second Life and Reaction Grid at the same time on a single screen. Not too practical, but pretty cool.