As I've got a G1, the speed isn't something I write home about a lot. Couldn't, wouldn't. However, with mobile processors getting smaller, cooler, and faster, I think Google is on to something with speech, search, and services.
Just yesterday, Google improved on what I thought was a decent start to voice commands. Here is a quick video of the set of Voice Actions for Android.
Is this going to be a game changer? Probably not this year or next but as Google improves on this, I think this will make a huge change for mobile computing. After all, mobile devices aren't exactly known to be easy to type with, at least, not compared to a laptop or netbook with keyboards.
However, if Google can improve speech recognition to the point that we can do everything mobile through voice, we may end up on the doorsteps of a new golden age in computing. Imagine driving with your Android in your pocket and yet need to send a message to someone. Just command your phone, dictate the message, and send.