Ok, so this is an older thread, but now that I've ridden the M8 a bit and have a friends that own them, I thought I'd add my observations
Some pro/cons are personal preferences, some are hard facts and a few are unknown.
My observations:
1) Fact, the M8 is smoother and quieter. Some like this, some don't because they like the traditional "Harley" feel. I fall into the 2nd category at this point but may come around one day...
2) The base M8 has more torque than a stock 110. How many of us have stock bikes? On 110's you can pull the cat, put on a fulsac or FM headpiece and get to where the M8 will be. Do this on M8, you void the wty.
3) As in #2, any modifications to the engine will void the wty, unless using EPA compliant parts and most like done by HD only.
4) The M8 runs cooler. I believe this is true. My 110 dual cool is hotter that any other motor I've owned. Just about everyone I know complains about the heat from the 110. I live in FL. I deal with it. In fact I'm now considering a 117 upgrade, because I think I can squeeze a few more BTU's out of that furnace.
5) M8 is the future of Moco. No going back
6) Suspension - while HD says the new suspension is "far superior" to the original Rushmore bikes, I don't think there is all that much difference. In fact, those that have had Ohlins (or other decent suspension) think the new HD suspension is a joke. Two of my ridding buddies have trashed the '17 shocks and installed the good stuff. If your current bike has improperly inflated or worn out suspension (can happen over 25K miles) then the new bikes may appear to be vastly improved.
7) Engine reliability - the jury is out on this. Quite a few reports of early M8 engine problems (oiling). But then again, lots of complaints about 110 lifter issues. Of course there are those that have never experienced those problems on either engine. My 110 has 40K and no lifter issues. But this is the only bike I've ever taken a five year extended service contract (just in case).

Colors - very personal. I absolutely dislike virtually all the new CVO colors, except the Black Fade out CVO ultra. Other love the new paint schemes, so that's an individual choice more than anything. Some of the paint actually looks like stick on labels on some of the color schemes. While that isn't the case, I think it cheapens the finish. (Personal feelings only)
9) Value - Hmm, hard to quantify this. If you are paying 50K+ for a CVO, you want what you want and don't care about value. Depreciation on that purchase will be fast and painful. But the introduction of the M8 has hurt the 110 values. I've been in that 1st category most of my life, but as I'm approaching retirement, I'm less inclined to make those type purchasing decisions any longer.