Hi Reed,
I couldn't find the link in your article about the 45-175 being a bit softer. Just OdzBodkinz's post with his flowers.
I did post a comparison at DPR a few weeks back:
45-200/45-175/40-150 the winner is...: Micro Four Thirds Talk Forum: Digital Photography Review
And someone else around that time was doing some blog entries with comparisons as well.
I did not find the 45-175 to be a big optical improvement over my 45-200. More of a trade. The 45-175 does appear to handle flare better, and in normal shooting this appears as slightly better micro-contrast. On the other hand, at least at infinity focus, the 45-200 appears to be sharper in the corners and edges than the 45-175. I'm not sure one would evaluate one or the other to be better - just a different balance of optical parameters.
Now, what certainly is different is the size and weight. The 45-175 is more compact and lighter for sure. And of course the cost is different as well, but not huge in my book.
I found the 45-175 IS to be ineffective at typical shutter speeds. Does well at very low shutter speeds where you don't expect perfectly sharp results, but in the 1 to 2 stops below hand holding range it doesn't help at all - same success rate turning it off.
So, the 45-175 was a bit of a let down for me. I stuck with the 45-200. It still is a good lens if you realize it doesn't have very good IS and consider the slightly improved micro-contrast to be a benefit compared to the slightly reduced edge sharpness. If size and weight matter (and for many of us in m43 land it does) then it brings a lot to the table (or rather it doesn't and that's a good thing). Still, in the end, I stayed with the heavier 45-200. It seems the QC on the 45-200 might be poor, and so for anyone that had a lemon of a 45-200 I'm sure the 45-175 is a vast improvement.
Link in my DPR post above to a giant gallery of comparison shots between the 45-200, 45-175 and 40-150 all at infinity if you are interested in obsessing over 100% views!
Ken