I am an Adobe Certified Expert in LR4 and I regularly teach LR4 classes, so I figured LR4 would be AT LEAST as good as Olympus Viewer2 when processing raw files from the OM-D E-M5... the results of my comparisons have really surprised me.
I did a couple of videos recently to show the difference between the two conversions and then to demonstrate how to set up batch processing in Olympus Viewer 2. The Oly software is too painfully slow to use for any serious editing,but it does a great job with raw processing.
Comparison video...
Olympus Viewer 2 vs Adobe Lightroom 4 | Rob Knight Photography
And the batch processing tutorial...
Olympus Viewer 2 Batch Processing Workflow | Rob Knight Photography

Cheers!

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Panasonic GH3, Olympus OM-D EM5, Infrared PEN E-P3 bodies. Oly 12-50mm, 12mm f/2.0, 60mm f/2.8. Panasonic 25mm f/1.4, 12-35mm f2.8, 35-100mm f2.8. Rokinon 7.5mm fisheye

Interesting, I need to play with this a bit.

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I wonder if you would give us your opinion of the Photo Ninja raw processor for OM-D raw files. I've just started using it, having tested it last fall. In re-processing several images compared with Lightroom 4 and Aperture 3, I find the Photo Ninja processor is preferable, particularly with very difficult images that had a wide dynamic range. In particular, reprocessing bracketed sets for later HDR work has yielded very visible improvements in my testing thus far. But I'd value and expert's opinion.

I haven't tried that, but I will download it and check it out.

I've had a similar experience to what you describe with Olympus Viewer 2 compared to LR4

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Panasonic GH3, Olympus OM-D EM5, Infrared PEN E-P3 bodies. Oly 12-50mm, 12mm f/2.0, 60mm f/2.8. Panasonic 25mm f/1.4, 12-35mm f2.8, 35-100mm f2.8. Rokinon 7.5mm fisheye

I've been playing with Rawtherapee which seems to handle EPL5 files ok, but the results are a bit patchy in terms of colour-casts, noise reduction and contrast. I'm planning to take a look at DxOmark and LR to see what they do. As you say though, Viewer 2 is painfully slow and lacking features, but the results are excellent.

Could you maybe post a sample or 2 of LR in comparison to Viewer2?

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Paul
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OM-D, E-PL5, O9-18, O14-42, O17 f1.8, O45 f1.8, O75 f1.8 P100-300, Cosina 100mm Macro
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The video shows a fairly typical comparison between OV2 and LR4. If you batch prices the raw files to 16bit tiffs in OV2 you don't have to deal much with the slow interface.

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Panasonic GH3, Olympus OM-D EM5, Infrared PEN E-P3 bodies. Oly 12-50mm, 12mm f/2.0, 60mm f/2.8. Panasonic 25mm f/1.4, 12-35mm f2.8, 35-100mm f2.8. Rokinon 7.5mm fisheye

Videos don't work here, but I assume you weren't using the Adobe default settings for raw conversion?

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E-M5 | E-PM2 | mZD 12-50 | ZD 12-60 | P 14-42 X | mZD 40-150 R | PL 25 | mZD 45

I didn't know if I should embed the videos, so I just posted links to them...
The comparison is adobe default settings vs the OV2 default, which is basically the in-camera settings.

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Panasonic GH3, Olympus OM-D EM5, Infrared PEN E-P3 bodies. Oly 12-50mm, 12mm f/2.0, 60mm f/2.8. Panasonic 25mm f/1.4, 12-35mm f2.8, 35-100mm f2.8. Rokinon 7.5mm fisheye

Vids work fine for me on firefox and chrome - didn't try IE.

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E-P1 now displaced by E-M5. GAS has passed. Critique is welcome but better make it harsh or I won't take you seriously.
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interesting read... is it possible to get similar results to OV2 by adjusting the settings in LR4? I now have gotten used to LR4 for cataloging, and I like how it's nondestructive. Using OV2 will just add another step to workflow.