Typically, former Android and WM6 users complain about "wasted" space because those platforms let users cram lots of stuff onto a single screen. WP is taking a different approach. I hate to say that it's quality over quantity, but it's at least close to that. It is worth noting that the switch to 1920x1080 will give you another row of small tiles, just like the HTC 8x and newer Samsung devices have; that's because the aspect ratio is taller than the 1280x768 used on the higher-end Lumias.
It took me a fairly long time to stop resenting that my main screen on WP7 didn't have the 38 touch targets that I did on Windows Mobile 6, but I now prefer the less cluttered look. Before WP, I spent more time scanning the main screen than was needed because there was just too much stuff visible at once, presented in different styles and sizes. Consistency and judicious use of space solves this, albeit at the expense of information density. It's a trade-off that I'm willing to make.
Further, my top tiles are both medium-sized so that I don't have to reach my thumb all the way to the top to start those apps when using the phone one-handed. While I do have a mix of sizes, I keep the small ones farther down the screen to prevent overload.