M8 user here. Came from a Samsung S3. Great improvement, Battery lasts for ages (for a smart phone) very fast, intuitive, crash free, robust, nice item in itself, splashproof too which is good. Camera’s not a zillion megapixels, but great for quick snaps.
For those that question the size, it’s big for about the first 10 minutes of use, then you just don’t notice. It fits easily into your pocket, which is the acid test. I’ve got a tablet and never use it these days, just use the phone around the house for internet etc.