I have an Xtrons unit. It's great, so far.
No idea bout the no warning sound when the headlights are left on. I've never had that. I get a ding when I leave the sidelights on, but then the headlights switch off when I leave them on. The sidelights don't, hence the ding.
Reversing sensors do change in speed, and even provide a radar on the screen. However the solid beep is not there anymore unfortunately. I have a reversing camera fitted, which I will admit is useful.
Long boot up times?
From cold, the unit boots in about 20 seconds (and that's probably me rounding up), but more to the point, once it's booted, it warm boots on ignition. Instant boot. As in, half a second and it's booted.
I don't know if the Xtrons is better than the Eonon, but I really can't knock it so far.