Some thoughts about what Olympus seems to have gotten right and wrong with their first Micro Four Thirds camera:

What they got right (in no particular order):

• Image stabilization (IS) in the body: Olympus leaves IS out of it’s its smallest DSLRs, so I was concerned they might leave it out of the E-P1.  They didn't.
• Size: As expected, the E-P1 leverages the compact potential of Micro 4/3 in a way that the Panasonic cameras have not.
• Dust reduction: All interchangeable lens digital cameras should have this; unfortunately, not all do, but the E-P1 does.
• Looks: Obviously subjective, but the silver and black E-P1 looks great to me.  Would be nice to see an all-black version as well.
  
• Image quality: This is a very preliminary impression, obviously, and made without any RAW files to examine.  The pre-production sample JPEGs at DPReview and elsewhere look very good and seem to support Olympus' statement regarding the use of a lighter antialiasing filter.  High ISO performance also seems to be quite good for this format.
  
• SD/SDHC memory card: Many thought Olympus might have gone the xD card route.  Thankfully, they did not.
• VF-1 external viewfinder is bundled with the E-P1 + 17mm lens kit (according to the latest press release).
• Movie mode allows manual aperture control.
• Battery is the same BLS-1 lithium-ion battery used in the Olympus E-620 and ought to provide better than average battery life in this camera. 
• Shot-to-shot times are short according to DCRP.

• Weather sealing/resistance
  
• Multi-aspect ratio sensor like the one in the Panasonic GH1
• Optional add-on EVF
• Distance indicator or focusing tab for the 17mm lens. Olympus missed a great opportunity here to control their focus-by-wire manual focus system based on focus tab positioning.  What a difference that would make for documentary photography!
• MP4 (eg, H.264 MP4) would have allowed better video quality/file size.  Instead, they opted for M-JPEG (.AVI) format, presumably because this older format is more widely supported. 
• A faster 17mm pancake lens would have made it much easier for me to pull the trigger on ordering an E-P1 kit.  Instead, I am tempted to wait for this lens on the Panasonic road map:
  
  In 35mm photography terms of framing and depth of field (DOF) control, it's the difference between a 34mm f/5.6 lens and a 40mm f/3.4 lens.  The Olympus lens should be available sooner and may prove superior, but nearly 1.5 stops more light and greater DOF control is difficult to ignore.  That said, one has to wonder what Panasonic is sacrificing to make a lens that fast yet that small.  We'll know soon.

• LCD resolution (230k dot) is below the current standard for high end cameras.  

• Autofocus speed: There have been conflicting reports about this in the existing previews.  However, most of the reports are not super-encouraging (eg, DCRP).
  
• 17mm f/2.8 lens rendering: DPR published a whole series of sample images with this lens, yet the lowest f-stop they used was f/6.3. Update: two photos at f/2.8 added here and here.  Lenstip.com has published samples here.
  
• Shutter release sound: As the Panasonic G1 shutter sound was disappointingly loud to many some (not me), it will be interesting to learn about the shutter sound of the E-P1.  Update: Imaging Resource has a comparison between the Leica M4 and E-P1 shutter sounds (link).