I spent a morning yesterday with the EM1 and really enjoyed it. I used the 12-40 2.8 plus my own 25mm Voightlander, Pan 14mm and an Oly 45mm 1.8. My main purpose was to try it for the video as I assume the Image quality for stills will be excellent. Unfortunately I shot in RAW and of course when I got home my version of Lightroom would not open the files! Need to upgrade....
However I do agree with Cooter that these cameras really are good with the small light prime lenses, and for me shooting with two bodies really does work - especially in situations where you have to react quickly. You did say the camera was for travel photography and of course that could mean a day out or a longer trip. If the latter, surely you would take a spare body anyway. That also gets round any waiting for servicing.
The olympus 12-40 is a prettier design than the panasonic 12-35, though I couldn't really tell the difference between the quality of the two and since I own two of the 12 to 35mm 2.8 panas I didn't buy the oly version, but one reason is I don't like zooms and 2.8 is just too limiting on these 4/3 cameras. The slowest should be f2 and everybody has their own style, but I firmly believe zooms affect the way you work.
It's a hassel but I'd much rather just use primes and that's pretty easy in the size fo m43 lenses, though somebody really, really, really, really needs to make a 100mm f2 or faster lens for this format.
As I've said before the em-1 is a better camera than the em-5 but the em-5 shoots prettier, though I haven't explored the em-1 as much as i would like.
One thing the em-1 does fairly well is video. Much better than the em-5, much better than the sony A7 and A7r, though not as good as the panasonic gh3 and the em-1 is still locked in 30 fps and 60 hz which means flicker in practical lights in europe.
A lot of photographers raised in the digital age don't know how film looked. To them the standard look is Canon on nikon dslrs which are somewhat overly smooth and somewhat global in color. Also digital tends to pick up a great deal of ambient color. In other words a brown room makes for a brown photo, even with specific lighting. The olympus look more like film, in the fact film was kind of dumb. It saw what it saw and didn't usually pick up ambient color. Also with film, once you learned a specific film you knew how it would react regardless of setting. (That one is hard to explain but you know it when you see it).
As I mentioned I'm now processing a thousand stills mostly from the canon 1dx some for the em-5 and get to a olympus file it's just a few seconds of corrections and the color is not global it's specific. The 1dx file in the same setting takes more work, if your deceserning in the look you want to achieve.
Now this one blows me away. i'm usually not one to say this camera costs less than that camera, but for a $1,200 camera (the em-5 I bought new) vs. a $6,000 Canon there should be a difference titled towards the higher price and in image quality there isn't, it's the other way. maybe the Canon has a fraction more noise reduction and a fraction more detail (on this I'm really not sure), but the look is not near as nice or specific . . . or film like.
Obviously olympus is on to something good, because Sony and Fuji have tried to emulate the look. I don't think they'll hit the built quality, but the looks like a camera style seems to have caught on.
I hope Olympus takes this another step forward, staying with m43 but upping their lens offerings and more controllable video.
I'm sure there is pressure to go full frame, but so far I haven't seen anything to suggest the full frame cameras have anything on the olympus, but if they do, I think they should go all the way and go larger than 35mm for a super omd, something like a Leica S2 size.