What are some alternatives to Quicksilver? I'm an avid fan of QuickSilver, and I had been using it for several years already. But then development of the application seemed to have stagnated for a while, and many bugs (specially with plugins and advanced features) were never fixed. I then moved to QSB, which seemed to be where the efforts were being concentrated in order to produce such an application. But then again, development seems to have stopped and several features I still miss (like AppleScript launching) were never properly implemented.

I'm aware of a few alternatives out there, notably AlfredApp and LaunchBar, but I wanted to ask here for your opinion and recommendations before trying them out.

So my question is, as of today, which would be the best replacement for QuickSilver? Ideally I would like support for the following features:


Launching applications, preference panels and apple scripts.
Web search, and search within bookmarks of my favorite browser. 
Able to perform actions or operations on files (copy, move, reveal in Finder).
Custom web searches are a plus. I would love if it could index, e.g., my delicious bookmarks.
Free. Open-sourced is a plus.
Some plugin infrastructure.
A healthy community of developers actively maintaining the application.
Not too many bugs.


In your answer, please do let me know about the features of your suggested application, and note if there are any missing features from my desired “ wish list”.
Alfred is the one that meets pretty much all your needs.


Launching applications, preference panels and apple scripts.
Web search, and search within bookmarks of my favorite browser.
Able to perform actions or operations on files (copy, move, reveal in Finder). paid version only
Custom web searches.
Free.
Plugin infrastructure.
A healthy community of developers actively maintaining the application.
Not too many bugs