Originally posted by bxf Agreed, satisfied users tend to not complain. Still, I understand that the two issues are real and not particularly rare.
I have had my K-3 since early April and have used it for flash photography periodically since then. The first I became aware to the flash lag was when I read about it here on this forum. I guess that gives some indication of how serious the issue is in general use. The lag is perceptible, but not obvious and may be an item of concern for some use cases. I don't know if similar behavior is present with other brand cameras.
As for rarity...as in my comment above, I have not read of any K-3 that do NOT have flash lag. In regards to the runaway mirror issue, the incidence was never high* and evidence is that it is extremely rare to non-existent in recent production cameras. A good indication of seriousness of the runaway mirror issue would be to take a look at RiceHigh's blog. He has a long history of continuous criticism of Pentax product, but the runaway mirror issue warranted very little attention from him. The same is true of the flash lag behavior.
In regards to your purchase decisions...If either of these issues are deal breakers for you, an alternative brand/model of camera might be a good idea. Be aware, however, that Consumer Reports members report that 4% of recent purchase Canon and Sony dSLRs and 6% of Nikon dSLRs had fatal or serious issues requiring repair or replacement. Yes, that is 1 of 20 boxes going out from your friendly local camera store.
Edit: If you do decide to purchase a Pentax dSLR and live in North America, I would suggest also buying the Pentax two year warranty extension. I say this, not because the cameras are prone to failure (they are not), but because it is such a good value at less than $20 USD.
Steve
* Be aware that there is an amplification phenomenon in relation to product issues on the Internet. People who post their problems to the forums typically belong to more than one forum and often re-post their complaints multiple times in multiple places. This is both good and bad. It is good because it encourages other people to describe the issue and assists the makers in characterization of what is happening in the field. It is bad because it creates the illusion of a pervasive problem when the actual incidence is very low.