The reviews to date have been utterly devoid of useful information.
I have read in a couple of places that the M1 is "faster". What the heck does that mean - and how does it improve things? Faster processor? Wheels and an engine?
Reading between the lines I reckon this is the same hardware as 350 but added wifi and on a different box with a new name and running exclusively through the new desktop app, so maybe intended more for new first-time customers than people looking to upgrade.
After a bit more digging, it looks like there may be updated processor: http://placeshiftingenthusiasts.com/vixs-powers-latest-slingbox-m1-and-slingtv-tv-anywhere-products/
If i was to guess, the M1 is using the same processor as the current SB 500... which is the xcode 4210. (See this old press release: http://vixs.com/press/Sling%20Media%20Press%20Annoucement.pdf ) That is just a guess, but it would be nice know for sure. I'm probably going to pick one of these up to replace my 350. Let me know if anyone else has any more info on updated specs...