It's big, bright, ugly and too simple. Too much color ("explosion in a paint factory") - I prefer largely monochrome w/occasional muted color highlights. Buttons and other widgets are too big, generally there's too little on screen simultaneously. Visually, I much prefer the look of, say, the Kit Kat UI. Material1 definitely looks like a Google app and that's not good IMO.
If it helps you understand my viewpoint, I'm a unix sysadmin and I like a technical approach. I'd rather have functionality visible, not hidden. After all, it's not "just a phone" or "just email", really - It's a computer that happens to fit in your pocket and merely has (among many other things) telephony, networking, graphics, etc. I don't often use it as a casual "quickly check this or that" device, I treat it like any other computer. After all, with computers it's as much (or more) the journey than the destination.