long post ahead!
since we first know each other from the fuji-x-forum, it's probably no surprise to you, rybolt, that I'm also a fuji user. I started with the fuji's a few years back and really quite enjoyed them. X100s, Xpro1, XT1, and a host of lenses. I really wanted to love the hybrid viewfinders, but what it boiled down for me was that there was no real confirmation of what they had focused on. I also didnt like the focus by wire. It was tolerable in EVF, especially on the XT1, but it wasnt what I would call "an enjoyable tactile experience". More of a means to an ends. Though I will say, I was never left wanting with the fuji lens quality.
What I learned in shooting the fuji's is just how important the photographic process is to me. While the results (a digital image, a print, a photo book, etc) are very nice and I enjoy them, the reason I shoot is to shoot, especially with the lack of a real darkroom side of the process. The fuji's just werent as enjoyable as they had once been for me, especially after the many firmware updates on the XT1. It just got too complicated, too many menus, too many options. I just wasnt willing to put in the time to learn it. And even if I was, there'd still be a bunch of layers of things that just "get in the way" between me and the scene\subject.
So I sold the XT1 and most of my lenses. I still have the x100s and xpro1 along with the 18/2, 35/1.4, 27/2.8, 60, and 8/2.8mk2, but I havent been using them at all. So I'm considering unloading everything, unless I go and convert the xpro1 to full IR.
Switching to the M system (240/246) for me has been a breath of fresh air. They've been freeing to me in that I can just shoot and not worry about what AF mode I have on or what film simulation or what DR setting or if I have the left or right eye detect on. What I've also discovered in this process, is that I've been shooting a lot more, more consistently, and I've been enjoying myself a lot more. All of this has resulted in what I feel is a positive feedback cycle in that I feel my photography has also improved since switching. I.e. my results improved without me really focusing on trying to do that.
Regarding the monochrom conversion from a color Fuji sensor or a color m240 sensor, really, it's about the same for me. Slight differences, but most of the same things apply. The large difference is that i no longer shoot jpg like I did on the fuji's 97% of the time. I've never tried jpg on the leica's to be honest, but mostly because on the 240 it struggles a bit with white balance and color and on the 246, well, it sort of defeats the purpose of this camera to shoot only in jpg. I will say though, I used to do the same fuji jpeg to SEP2 process, and while I loved the results, i hated the workflow of needing 2 files and 2 programs. Since getting the leica's ive backed off a bit and developed a preset that mostly emulates what I want out of the SEP2 results. So now I also spend less time on the computer....though I could have done this with a fuji as well.
The results from all the cameras have been totally acceptable to me. The leicas are usually "better", but honestly, I'm not sure it's enough to get me to switch from the fuji if you asked me to blind choose based off image samples, perhaps with the exception of the 246 which is just a wonderful camera. I'll also say that I no longer even have to think about sharpening settings and x-trans detail issues (foiliage, high-iso smearing, plastic skin, etc), which while rarely an issue for me, did present itself on a handful of occasions. I will preface this with saying that I'm unusual in that I think most of these new cameras with more and more megapixels are of little interest to me. I feel either fuji or m has really obtained with 35mm film was about in providing "good enough" detail for enlargements in a portable size. While it falls short in DR it is way beyond in high iso. Maybe one day we can have it all on digital.
For your m9, I'd see if they would offer you an upgrade to an m9m or m246 if you are truly considering this camera as a b&w only camera. Though maybe you want the m9 for the colors people seem to love from the CCD, though honestly, David Farkas from reddotforum did a solid 3 part review of the color differences that showed it's possible to get pretty much an indistinguishable result from the m240 with simple tweaks. And the 240 series is a nicer camera in actual use.
And last but not least, for a travel camera, it's a toss up in my opinion. I know you like to go on vacation with the sole purpose of shooting a lot and with a lot of varying focal lengths. In that respect, the leica is clearly inferior. It's heavier, inherently limited to prime or variable lenses, and focal lengths below about 90mm in practical use. The EVF attachment or using LV is clunky and not enjoyable, so I never use them. They're significantly more expensive if they are stolen, damaged, lost. It will take a bit of discipline I think to change what you bring.
On a recent trip of mine I brought both 240 and 246, but then only a 28 and 50 which lived on the cameras. I swapped them occasionally before going out for the day, but that was it. Kept things simple and in a small camera bag. I needed 2 filters which were the same diameter, so those could also live on the lenses if I needed them to, so as to avoid needing filter cases. The batteries lasted for days of shooting, not hours, so I needed fewer batteries and spent less time charging, except when I forgot to switch the camera off in my bag and it took 500 pictures of the inside of my bag. haha. When I traveled with fuji's, I bought like 4-5 batteries for each camera and on occasion went through a few in a day, and I dont really shoot that much. (maybe I avg about 100 a day?)
i should probably stop typing now before this gets too crazy
but if you have any other detailed questions i would be happy to try to answer or give my opinion
feel free to use email as well. "My user name here" AT gmail