DSLRmagazine is the very first website to post an Olympus XZ-1 review (Click here to read the google english translated text). They made a very detailed and accurate test. Those are a few interesting discoveries:
– The lens resolution is very high at 28mm and wide open (f/1.8)! Resolution decreases on the tele end.
– Moderate distorion at 28mm
– Moderate Vignetting at 28mm and f/1.8
– Very good autofocus and metering!
– Veyr good image quality up to ISO 800.
UPDATE: pcpop posted a XZ-1 review with many image samples.