LookOut is OE integrated only (which is evil). Sure, it searches other things as well, but clearly Microsoft screwed up when you have to use a program within a program to finally get a decent search in Windows. LookOut + Outlook feels pretty bloated too.
In the end, I have a feeling that this is another 20% of some Googler's time. This is a geek toy with minimal penetration meant to keep the Google Groupies happy. It might become big or it might become stale like the Google Deskbar.
Lastly, I have to add that I am sort of pissed off that I have the Gmail Notifier, Google Deskbar, Google Desktop, and Google Toolbar (i don't use IE but it's there), Picasa, and Hello all installed and collecting various informations about me (which I don't mind, they obviously put it to good use). The problem is that, although they all have a central contact point, Google Headquarters, they don't talk to eachother. As a matter of fact, why aren't they optionally combined in one install application?