The marketplace for screen capture tools is starting to get quite crowded, but PlayClaw stands out as it strikes a great balance between ease of use and quality. The main competitors are Bandicam, Fraps, and Dxtory. PlayClaw beats Fraps as it is much less resources intensive, and produces higher quality ouput than Bandicam in most cases. Using PlayClaw usually results in nothing more than a 1 to 5 frame rate decrease and very few dropped frames during recording. Dxtory, coupled with the Lagarith codec produces slightly better results, and is even less resource intensive, but takes a bit more effort to set it up; in contrast the PlayClaw UI is very easy to navigate.
The main features are: Record in-game footage. Record the desktop. Buffer a period of footage (from 5 to 600seconds). Take screenshots. Configure input from multiple audio sources including mic. You can also stream to Twitch, YouTube and Customer Server (not tested yet)
Recording desktop / in-game and activating recording to capture the buffered footage never show any interuption or performance hit. I have tried streaming to a 10,000prm HDD, and also 5400. As with all capture tools the faster the hard drive the better, but footage was still OK on the slower drive. Being able to define the number of CPU threads the software utilises really helps performance. Other essential options are the ability to define frame rate for capture and set the resolution (although I would recommend recording native and then scaling during editing).
One thing I really like is the ability have PlayClaw write audio tracks in seperate files. This makes it a lot more convenient if editing audio as each each source (in-game or mic) gets it's own file. So no bother with extracting audio from the video file, or having all audio streams mixed.
Taking screenshots produces a nice overlay effect - it really lets you know a shot has been taken without being intrusive. Other overlays can be configured to show frame rate, recording duration, buffer, a clock and many other features. One of the most useful overlapys shows how large your recording is.
The main area where PlayClaw could improve is around the MJPEG codec. It appears they use their own custom codec and many have found it can be a pain finding editing software to support it. (Protip - If you have problems opening the files in your editor, try installing the free version of Bandicam - this will install / update the codecs - it certainly worked for Sony Movie Studio 12 and 13). It spoils what is otherwise a very easy to use application. It would be nice if they supported advanced options that allowed the user to install their own codecs. Edit: The developer has kindly clarified the MJPEG issue. But out of all the capture software I have tested over the years, PlayClaw is the only one that caused problems like this. So I am not changing my comment, as many people have found my 'pro tip' useful.
Overall PlayClaw is a great piece of software. I am using it exclusively to capture footage. It does a great job.
Edit: May 2015 - Slight changes to incorporate questions received below