I like the interface for it's image search and I'll use it when search for wallpapers (since I can easily select a large size) or I need to specify other constraints quickly. Looks good for videos too. But in terms of a normal web search it doesn't seem to have a huge advantage over Google from my perspective, and as for the shopping / maps / possibly others that I haven't looked at, it just directs you to other sites, some of which have lots of ads - eurgh.
Thumbs up to Microsoft for the image / video interface, I like it. Thumbs down for cheating (at least for now) on the shopping and maps searches. And it's pretty neutral for everything else - ok I guess, but nothing that's going to give Google too many headaches.
I think it's good they're trying to get something out there though, competition generates more progress = better searches for us!