I'm not sure if local search is really the new killer app, but I've got no shortage of options at the moment. I needed to find all the emails I've received from WasteIndustries. I ran all three searches at the same time, pitting the various search tools against one another.
I started Outlook first, because I knew it was slow. Next, I started Lookout, because it's convenient, right there in the Outlook toolbar. Finally, I double-clicked on the Google Desktop icon in the taskbar and waited while a browser opened up.
Google Desktop came back almost immediately with six hits. The downside of Google Desktop (aside from the fact that it's a long name to type every time I mention it), is that it doesn't provide native access to these items. If I want to open, delete, or move these emails, I have to click once on the item in the search results and then on "View in Outlook," not to mention having to go back to the search results for subsequent items. It's fast and powerful searching, but it has the disadvantage of being browser-based.
Lookout finished a close second (although it wouldn't have been as close if I had already had a browser open to Google Desktop). Lookout's main problem is that I can't delete items from its search results list. Very often, I'm trying to whittle away at the *mumble mumble* thousand emails in my inbox (okay, so I'm an email packrat — according to Lookout and Google, that's okay, so leave me alone), and Lookout's search is nearly worthless for that, because I can't delete what I find without opening each item and deleting it manually. If they would fix that, Lookout would be the top choice for email searches.
Outlook search was just sad. I let it chug along for about a minute, beating the crap out of my hard drive, and then I just stopped it. When it finally finds what it's looking for, it's the best, because its search results list items are just like the items in the inbox itself. You can delete, flag, mark as read/unread, etc. They are native Outlook email objects.
Too bad there's no way to pipe Google Desktop's or Lookout's search results to Outlook, so you could combine the best search with the best native item handling. More and more, I think we'll see that kind of integration become possible, as software becomes more service-oriented and pluggable. Google Desktop could be a search service that feeds to an Outlook item list service. All we have to do is re-engineer every piece of software that's ever been written, and we're good to go.