I often wonder (don't regret really, just ponder) what it would be like to have just the best custom kit for each job*. A specialised landscape, sport and street/travel kit.
One lens/camera combo that I would have kept for that thinking, if that was how I chose to go would have been the Canon 1Ds mk2 and the 400 f5.6L. The lens, like my other favourites from Canon, the 70-200 F4L and 135L, was not stabilised, but it hand held well, easily lower than it's reciprocal focal length/shutter speed equation.
The OMD sensor has similar properties and the same pixel count, but the quality out of those old Canons was way better than anything I had seen before and the colour more natural than the lush colour of the current crop (much like the Olympus look). I remember showing a friend, a 5d mk2 user, an 8x10 of the above and telling him the long list of compromises made to get it. I don't think he believed me until I showed him the "full monkey".
Ahwww, cute. 5d Mk2 and the same lens.
The lens was a giver. I remember trying to convince a customer to buy it over the 100-400L, but he went with the versatility. He later regretted the decision after we compared identical images from similar cameras. To top it off, after selling it and the 135L to a shop in a neighbouring city, I found out from my wife, that a friend from her work bought them both and has them back here. Haunted still.
The Olympus glass is the equal of the Canon I had (the 45 is nearly identical to the 85 f1.8 in look and performance, but less than half the size, the 75 matches or beats the 135L, 40-150 is better/faster/longer than the 70-200 f4L and the 75-300 surprisingly close in end result to and easier to use than the 400 and a little longer), but if I had held onto those lenses they would have been (were) the nucleus of a good SLR sports kit.
*Fuji for landscape (14, 18-55, 60 and 90 macro), Olympus for street and portrait (17, 25, 45, 75) and Canon for sport (24, 40, 135, 400). Selling and buying gear for me has been a bit of a merry-go-round and I don't regret most transactions, but some clear thinking in hind sight would have spared me from selling off a couple of camera and lens combo's that just worked.
The ideal is one kit that works (that I have), but it is sometimes fun to remember past successes, just not dwell too much on the ones that got away.