The ease of customization and the button / dial layout. After getting my hands on the camera and playing with it all day, I can tell you that the layout is awesome (for me at least) I am really enjoying the sheer amount of things you can quickly do with this camera - Coming from an EM-5 MKII the way the customization works on the Pen feels much more intuitive and simple. (and I still love the EM5!!) I love the C1 - C4 Custom modes on the dial and how much easier it is to customize this camera to quickly do exactly what you want. It really is way more intuitive than the old myset system without dedicated dials. It all "clicked" for me in a matter of minutes. (where I was always frustrated with my mysets on the EM-5MKII. ) For now I have it set up as: (this will change as I mess with the modes and make my own) C1 Regular shooting +Beep + IR / Aperture Priority mode / Mono mode 2 / Color mode 2 C2 Church Mode - Silent Shooting No IR, No Beep / Aperture mode /Mono mode 2 /Color mode 2 C3 Action-sports-wildlife / Aperture mode / Mono mode 3 / Color mode 3 C4 Astro / Long Exposure MF / Manual mode set to 20 sec Exposure and ISO 1600 / IDGAF / IDGAF I love that you can switch the front dial and each C1-C4 will individually remember the front dial mode you like (for example If I'm shooting in C2 and I switch to mono i can set it to remember that I want mono Mode 2 for C2. and say mono 1 for C3. For some reason with the EM5-Mkii I always had problems with the mysets getting messed up and problems trying to map the mysets to the unused dial positions without getting confused. The PEN -F is so much easier to figure out. And they are no longer even called mysets they are now called custom Modes. They are still basically the same as mysets but for some reason it just all works! I see myself using C-1 2 3 and 4 90% of the time I use the camera. Some other quick notes: Of course the camera is beautiful and my non camera friends who have seen it are all the sudden asking me about how much it costs to get into it. -The EVF is great so far and I am not noticing any lag compared to the MKII but I have only been playing with it for a day. -Mono Mode 2 Is sweet, It really makes normal mundane things pop and is really fun, Other color modes are on the dock to play with tomorrow. -I don't think I am going to need a grip with the camera but the biggest lens I would use without a grip would probably be the 75 1.8. the inner thumb spot works well with my hands and I just wrap my strap around my wrist if I need extra support. Ill have to use the camera for an extended period of time to really see if I can skip the grip. -So far the front mode dial does not bother or scrape against my finger too much- so far so good -I am really loving it and I cant wait to do some real shooting this weekend. Wish list for the Pen F - -Ability to name custom settings Example "C1 - Walk around", C4 Astro -Ability to save all settings to survive the major firmware updates -Maybe a different 3rd party grip? Things I don't like so far - The tripod jack seems to far forward. - no mic jack(which I knew about before buying but wish I had) I have some more shots taken with the Pen F on my Instagram: Triangle_Craft I Might post some more on here soon too!