have both
I started with the droid 1, I use it now primarily as a work phone, purchased an X about a month ago and it is a HUGE improvement. Most of the stock apps have a few extra tweaks for the X (nothing major, just noticeable).
The extra half inch on the screen is a very noticeable improvement. I have a lot of mp4 vids, so its cool to be able to play them on the tv set, also.
The ability to download alot more apps is nice.
The only downside is getting used to the different positions for the 4 standard buttons (originally on screen, now physical buttons). Other ergonomic issues, for me, is moving the power button to the center of the phone, rather than the right side...before was convenient for my thumb when bringing the phone in and out of sleep, now its a bit of a stretch.