DNG vs RAW in-camera

Just noticed the option to capture in DNG format rather than RAW on my new K5. On the old K100D I converted to DNG on uploading to Lightroom, almost never used the Pentax RAW converter, and didn't archive the RAW originals. Without getting into the usual RAW vs DNG arguments, I can't see any reason not to switch to the in-camera DNG option - but as usual I would value any opinions from the forum.

My older version of PS is'nt able to open the K5's RAW files so DNG is the obvious solution, I can't see any noticable difference and like you I save them as Tiffs once I've decided the " keepers " and delete the DNG's.

The newer cameras all have DNG or PEF as RAW files so we select either one depending on whether one uses Pentax Utility Software or Photoshop

RAW isn't a file type. PEF is Pentax's native RAW, DNG ia Adobe's version.
DNG is pretty much a standard now and probably best for archiving.
In other words, both DNG and PEF are RAW.

I switched to DNG years ago to avoid having to worry about sidecar files for metadata.
The K5 DNG format now uses compressed images which my K20d didn't. So its DNG files are approximately the same size as the PEF's. In the past I used to convert my K20d PEFs to DNG with Adobe DNG Converter (ADC) with a significant reduction in file size as compared to the native camera DNG format. Now that step is not necessary.

One other point. I like DxO Optics Pro as a raw converter. It is virtually automatic, and creates finished images requiring very little touch up. It does not support DNG files created by third party converters like Adobe DNG Converter. But it does support ALL camera generated formats - Pentax k??? among them. So it will read DNG files created with the camera, but not necessarily converted DNGs. It worked with my ADC converted K20d PEF's but it does not work with my ADC converted K5 PEF's.

The whole point to Adobe's DNG (Digital Negative) is that it's a standard format readable by all RAW converters now and in the future, particularly suited to archiving to be readable in future generations - so there really should be no problems reading a DNG from a camera or one converted with the Adobe converter. Not sure why you call Adobe's DNG converter 'third party' as Adobe are the inventor and they own it.
Some good info at Wiki: http://en.wikipedia.org/wiki/Digital_Negative