Yeah, they changed a lot of things, but I feel they kept its charm pretty intact. The movie was made on a budget of about $30 million, so they unfortunately didn't have a lot of funds to explore the entirety of the plot. It's a shame, I'd love to have seen more of M.
M was pretty swell, yeah. XD Actually, the only thing that really irked me isn't even too big of a deal- it was that Nora wasn't black. But that's about it. I would've like to see R's little zombie kids, but I guess it's okay.