I guess some of you have already read this:
Pentax K-5 II / IIs Review - Introduction - PentaxForums.com
Overall the impression is pretty good:
The K-5 IIs is an impressive camera, and it's the first APS-C DSLR of its kind. While we can't refute that removing the AA filter is an easy way for manufacturers to increase the resolution of a camera, this move shows that Pentax is staying true to their motto of "being different". In addition, the K-5 IIs is what added true appeal of the K-5 II launch announcement. Without it, we fear that many would be questioning Pentax's decisions even more than they are today.
It's undeniable that the K-5 IIs is capable of taking sharper photos than the K-5 in the hands of the right user. We will leave it up to you to decide how big of an impact this would have on your photography.
Thanks to its increased resolution, the K-5 IIs receives a 10/10 for image quality while the K-5 II and K-5 have been bumped down to a 9. We find that at the end of the day, the K-5 IIs's capabilities are not to be overlooked. NB: image quality ratings are within the scope of APS-C only.
Pentax K-5 II and IIs Pros and Cons (without looking back at the K-5):
+ Best-in-class image quality
+ Low noise
+ Weather-sealed body
+ Excellent handling
+ Superb low-light autofocus
+ Fast burst frame rate and 1/8000s max shutter
+ Intuitive interface with many dedicated buttons
+ Good value
- Overall performance is slow
- No manual video controls
- No focus peaking and sluggish live view
- Slow SD write speed compared to other brands
- 11-point AF comparatively poor for sports
- AVI video files can be tedious to work with
- Somewhat small body w/o battery grip
An added pro of the K-5 IIs is increased resolution, with higher risk of moire being the associated con.
The K-5 II is ideal for: outdoor photographers, still shooters, low-light outdoor applications.
The K-5 II is not so great for: action photography, video, and beginners.
Who is the K-5 IIs for? Enthusiast photographers who understand the risks associated with a filterless sensor design.
The Future and Who Should Upgrade
Pentax has future plans which include the introduction of a high-end APS-C DSLR as well as a full-frame DSLR. At this point, it's not a question of whether or not these cameras will come, but rather when. For those who do not want to wait a year or more for these advanced cameras and are currently using the K-5, it makes sense to upgrade to the the K-5 IIs. Similarly, those using other Pentax cameras will greatly benefit from the upgrades in the K-5 compared to older bodies such as the K-x or K10D, but may prefer to go for the cheaper K-5 rather than the K-5 II.