I have been thinking long and hard about this and I can only come to this conclusion.
It is a nice feature. It needs tweaks, so results for photoshop don't pop up, or if they do it should explain it's not compatible with Linux.
But what it needs more than anything, which is something Canonical keep missing out of all of their super new features is a simple tickbox for on or off. I understand that this is still beta, and it's certainly not LTS so it is more or less a testing platform, so I'm not jumping up and down right now. Canonical have proven to me that they can iron things out between normal releases and LTS, and I'm happy to accept that this may well be the case here. I'm basing this on evidence that I have seen over the last 4 years, not just what Mark says.
This really is a great step forward for UX, as it is saying "hey, let's do more 'cloud' stuff from the desktop." Think about what else will be possible with a bit of thought. We could have it bring up all of your photos, from all sources (picassa, facebook, twitter) and present them in one place. I could type something like "London" into my dash and it shows me all the photos I've taken in London, a list of all my friends who are currently *in* London, and maybe sell me a London guide book. I cannot begin to express how awesome features like this can be.
Amazon is only a single step to a full set of amazing features, and we must remember that these aren't *ads.* I am searching for a product, I can chose to buy it, and I won't get prompted to buy anything similar next time I fire up the dash.
One thing that I also think is important to remember, is that we are a set of pretty clued up power users and as such we will see problems and we will jump to justify why something is a bad idea. However, if I were to install this on my Dad's laptop tomorrow, I can guarantee he would actually be quite thrilled with this feature. This is Linux for Human Beings and I think product searching is a very human thing to have.