UPDATE:
After the update to C1 LE V3.6 for Windows has been delayed numerous times, it now has become available. It should be a free update for C1 LE V3.5.2 owners.
See rawworkflow.com
See forum at rawworkflow.com
Here you can find: phaseone.com

C1 LE
I use Phase One's C1 LE. Phase One's FAQ says, the manual is in the zip archive, but this is not true. There is no user manual. So we went through the help menus, which just sums up the menus and dialogs with no explanation. The help function appears to show old versions of the different dialogs and other features. It surely needs to be reworked.
In the near future, a user manual would also be welcome. It should not just sum up the menus-items, but also gives a good description of the different settings (including recommended settings under different situations).

Noise
I found more noise in the pictures that were converted from RAW by C1 LE than out-of-the-camera jpeg pictures. Canon has a very good in-camera noise reduction system. Their RAW conversion software (ZoomBrowser EX) has got the same good noise reduction build in.
In the past I wrote a program for the Minolta D7 RAW conversion. I used an adaptive noise reduction algorythm, with a treshold slider, that removed noise efectively, without touching details. It would be nice if such noise reduction system could be used in C1. For noise reduction, Noise Ninja or NeatImage are currently the way go instead of using C1.

Banding
C1 LE suffers from badly banding, in particular in nightshots, while Canon ZoomBrowser EX does not cause any banding. It looks like C1 LE takes only 8 of 12 bits/pixel out of the stored information in the RAW file. The sliders which should avoid banding did not seem to work. After selecting maximum effect, the banding was still there.

Conclusion
Pros:
- Nice workflow idea
- Nice to work with, once you got find out how it works

Cons:
- Major updates are NOT for free, you have to pay every time there is an upgrade.
- I seem not the be able to find out which is the current version from the phaseone website (secrets?).
- Needs better noise reduction and separate color and luminance noise sliders on an image by image basis, plus ability to turn off noise reduction (slider on "0"). Place these controls in a new tab called “Noise Reduction” between Exposure and Focus tabs
- Better sharpening algorithms, plus ability to turn off sharpening completely (slider on "0")
- Should provide the ability to type in the number for the slider values
- Cut/Copy/Paste/Move support like in any Windows app, including shortcuts CTL+C, CTL+V, CTL+X so that pictures can be moved around folders
- Remove the batch process limit, add a counter which dislays the number of entries in the queue
- Can't "grab" the image and move it with the mouse, have to use scrollbars for this
- Should provide an accurate percentage for the fit-in-window view
- Suffers from excessive banding in night shots
- Misses multiple Undo/Redo/History function
- Can't set separate Black, white and grey balance
- Can't toggle between "before" and "after" (including current edit and all edits) - The current cropping system doesnt recognise orientation
- Misses fine Jpeg compression settings with a quality in 1-10 range
- Histogram should be visible at all times when making adjustments (including curves)
- Zoomed image shows terrible jaggies. One could decide to deinstall the program after finding this
- No real full screen review of the image
- Preset cropping ratios, that are scalable up and down
- Lacks a file deletion confirmation box, which is standard in any software
- Delete should delete the THM files as well, not just the CRWs
- The sliders of temperature cannot go below 2000k whereas auto white balance can set them far below
- The cursor zoom (right click) doesn't work on the edges of the image
- Should put EXIF data back in the Capture tab
- Ability to choose what info is shown beside the thumbnail on the left, including EXIF info items
- Lacks multi-monitor support
- C1 doesn't want to be the default app to open a RAW file with
- Lack of keyboard shortcuts, of often used functions (File Browser)
- Should support relative path names in the develop tab
- Some kind of plug-in architecture with a SDK would be very nice, to get (better) 3th parties noise reduction and sharpening
- Should have Film profile settable as a default in preferences
- Option to replace cameras image prefix for every image in a collection (e.g. imgp1001/ imgp1002/ become jane1001/ jane1002/)
- Would like Tone Control sliders similar to X3-fill light and PSCS Shadow/Highlight
- Should have storage of settings files in subdirectory of raw file location
- Help file seems to talk about old versions
- Lacks decent documentation
- No bug reports, no bugs fixes scheduled
- The Canon D20 that is around for months, is still not supported.

Support
There is zero support. You are at your own with the bugs that C1 LE contains. I can't feel loyalty to C1.
New releases are delayed again and again.

Conclusion
My rank: "Below average".