I used Butler for a while and I liked it a lot. The pasteboard feature is really nice. Other than that I just used it to make a menu with different types of searches on it.

I stopped using Butler when I figured out how to replicate the pasteboard feature using Quicksilver's clipboard history plugin. At that point, it wasn't worth the extra overhead, since I'm already running Quicksilver as an app launcher. I wrote an article for Macinstruct detailing how to install and use Quicksilver's clipboard history plugin:
http://www.macinstruct.com/node/186

Note: Butler comes with pre-configured keyboard shortcuts that can conflict with you existing ones.
I didn't find how to get a list of all the shortcuts that have been set in Butler, so it's not that easy to find the entry to which the conflicting shortcut has been assigned.
However, in this case Butler's shortcut was useful (ie: skip to next track in iTunes) so I kept it over my existing one. :)

A good search engine to add: Wikipedia via google "I'm feeling lucky" search:
prefix: http://www.google.com/search?hl=en&q=site:en.wikipedia.org+
suffix: &btnI=I'm+Feeling+Lucky
This way your search gets recorded in your google history (if you're logged in).

(Adapted from Mycroft search engine.)

I really like the menubar adds for this app. the only thing is i didnt want to have to go in and attach shortcuts to all my apps... lol, im really lazy like that. usually, i just type in the first couple of letters for the app into launchbar, and hope i get it right.

Bar far, a very extensive and useful app if you want alot of menubar shortcuts.

One word: Absalutly Brilliant! Oh, wait. That's who. Oh well.

Please, folks, realize that Butler is donationware. Yes, it's one of my must-have utilities, it's an essential. And it's donationware, please consider giving back a little bit to the developer, even if it's only a mere symbolic sign of your appreciation ... I'm sure he'll be happy and even more motivated to develop more wonderful stuff.

now we are all going to sing: "
Peter Maurer is our hero, created this up, cost zero!
Peter Maurer, he is our god! Lets record this to iPod!"

Come on, you are more creative than I am, aren't you?

Best. App. Ever.

I used Launchbar, then Butler, then Quicksilver and then I went back to Butler.
Clipboard-history, a major selling point.

Calling Butler a launcher doesn't do it justice. It is a fantastic app and I would recommend anyone to check it out. I donated and used it for a long time, although I now use QuickSilver, which has improved dramatically in terms of stability and does run a little faster on my machine. Having said that, Butler still offers more features and is probably the more complete all-round package. Try them both and see for yourself which best suits your needs.