My current kit is in my signature but I'm looking to cull a few items. I don't find that having two bodies is worth the extra effort of carrying two bodies so my EM10 is already listed here as is my 25mm f/1.8. My original intention was to buy the 17mm f/1.8 when the 25mm sells. But yesterday I went and looked at the 12-40 PRO in store and loved everything about it except the size. 1) I'm thinking for street photography and walkabouts the difference between f/1.8 and f/2.8 won't be that big a difference. When shooting a whole scene where nothing is up close at around 17mm, the entire scene is pretty much going to be in focus either way. 2) Where it will make a difference is indoors. My 25mm is my go-to for kids birthdays etc. but its too tight and I can't zoom out with my legs any further. With the 12-40 I'll have the option of going even wider than 17mm but of course, I'll lose light gathering. 3) Finally, the 25mm is left on my EM5 90% of the time and I expected the 17mm to fall into that role. However, the 12-40 is significantly larger. Am I committing to having that beast as my default lens all the time and am I OK with that? I'm sure I'm not the first to ask this question here and I can do a search but sometimes its nice to get newer, fresher perspective so I hope no one minds that I started this thread.