Restaurant search provider BooRah launched an Anroid app last week and posted some details about downloads and usage:

We are also pleasantly surprised by the number of reviews we have received from the phone compared to our website and consumers seem to find it very convenient to write a brief review while at the restaurant.

The following chart shows the distribution of their application's downloads by geography, which corresponds to the T-Mobile 3G rollout:

And here's the distribution and volume of search activity ("unique locations where users performed searches for local restaurants. These do not include searches by cuisine, keyword or location separately"):

I finally got a chance to hold and play with a G1.

I want to caution that it was not enough time to render a final judgment. Many things were nice about the device, but it was not as intuitive and elegant as the iPhone. In addition its greatest purported differentiator -- the presence of the physical keyboard -- is also a weakness in some situations. There appears to be no virtual keyboard (or that I couldn't find). And so when you conduct a general mobile search, you have to flip the device into landscape mode and enter the query.

It would just be faster if a virtual keyboard came up and you could do it that way. For SMS or longer text entries the keyboard works well. 

Finally, I want to return to the BooRah comment about mobile reviews quoted in the passage above. The conventional wisdom is that people won't necessarily enter reviews when they're on mobile devices because of the awkwardness of the form factor. However I dispute this, especially if the reviews process is simplified (see GoodRec).

As I mentioned in the post immediately below, there's going to be a flood of local or location-specific content that will come online from people in physical places using mobile to capture and upload that information. Reviews is just one category.