I have and use my old favorite E-system lenses on the E-M1: ZD 11-22/2.8-3.5, ZD 35/3.5 Macro, ZD 50-200/2.8-3.5 (with and without EC-14 1.4x converter). At one time, I also had the Panasonic/Leica Summilux-D 25mm f/1.4 ASPH and ZD 50mm f/2 Macro, but I sold them when I off'ed the E-5 to the same fellow who bought that from me.
These were excellent lenses on the E-1 and E-5; they remain excellent lenses on the E-M1. That said, the Olympus raw converter included software correction profiles for all of them (and some of them need it), and the Summilux-D 25mm includes software correction in its firmware that is automatically embedded into all Micro-FourThirds raw files—it corrects for some lateral chromatic aberration. (The Panasonic/Leica Vario-Elmarit-D 14-50/2.8-3.5*ASPH does not have this feature.)
Instead of re-buying the older FT Summilux, I bought the mFT version because it was much lighter and, in my testing, produced results that are virtually identical. I also bought the Macro-Elmarit-DG 45mm f/2.8 ASPH instead of rebuying the ZD 50mm f/2 Macro because, again, after testing them both extensively, I found the Macro-Elmarit was actually a superior performer.
The ZD 9-18mm is a consumer grade lens, like the 35 Macro, and a good performer for it's price but not up there with the 11-22 (high grade), or super high grade, lenses.
The ZD 12-60mm f2.8-4.0 SWD is another high grade lens and perhaps a tiny bit sharper than the ZD 14-54/2.8-3.5 original lens in the system. The Mark II 14-54 has superior bokeh, however, and the ZD 12-60 in the hands is front heavy and has mustache shaped distortion at wide settings which is hard to remove ... Olympus' own lens profile does the best job of it, but it's nowhere as sweet as the ZD 14-54 or Vario-Elmarit 14-50 to my eye.
So if you're talking "optical" to "software", well, all these lenses were designed for software corrections to get the best performance out of them. The Olympus and Panasonic/Leica FourThirds SLR lenses are indeed beautifully made, superb performers (the ZD 14-35/2 SHG and ZD 35-100/2 SHG are probably amongst the finest of their focal length range ever made, as is the ZD 150/2 and ZD 300/2.8), never mind the ZD 7-14/4 SHG. These were all ultra premium, professionally targeted lenses and made the current range of mFT lenses seem rather inexpensive. They were all also double the size and weight ... The current marketplace doesn't want to spend that amount of money or carry that much weight for a FourThirds format camera, so they are disappearing.
I have great fondness for the E-System cameras and lenses, still have (and occasionally use!) my E-1 with the 11-22, 35 Macro, and 50-200. The lenses are all wonderful. As a camera on technical merit, the E-M1 runs rings around both the E-1 and the E-5, and the lenses work just as well with it as they do with the SLRs.
G