1. The 1800MP comes equipped with vertical keystone correction. This means that if you need to point the projector up or down you can fix the keystone effect. However, it does not come equipped with horizontal keystone correction. In order to get a square picture you need to make sure that you projector is centered with your screen. Otherwise, one side of your picture will be higher than the other.
2. You will notice that the Dell 1800MP does not come with either an HDMI or a DVI port. I was able to hook the projector up to my media center PC using a VGA cable and it looks great. However, the picture over the S-Video didn't look nearly as crisp. If you want a great looking picture consider getting a cable that converts component video into VGA.
3. The Dell 1800MP does not have very many options for zooming in or adjusting your picture size. This means that you will have to place your projector the correct distance from the screen in order to get the picture to be the right size for your screen. For my 106" diagonal 16:9 HDTV format screen I had to place the screen approximately 16' away from the wall. Before I mounted the projector on the ceiling, I simply held it up until I found the right spot where the projector would fill the entire screen.
4. A lot of places will charge you an arm and a leg for a mounting bracket. However, you should be able to pick up a reasonable bracket at an unnamed online auction site for about $30 including shipping. The one that I got has the ability to swivel the projector so that it can be pointed down or to the side slightly. This came in really handy when I was trying to get the projector image set up with my screen.
5. The menus for the dell 1800MP have a bunch of useful options in them that you will need. There is a setting that will flip the image so that your projector can be mounted upside down on the ceiling. There is also a setting that will change the aspect ratio of the projected image to 16:9 if you are going to use a widescreen display area. You can use these settings along with the contrast, color and brightness controls to fine tune the picture until you are happy with the picture. When your room is really dark you will see black bars above and below your screen since the 1800MP is not a widescreen projector by design. This isn't really a big deal but I thought I would mention it.
I am the first one to admit that the Dell 1800MP isn't as good as the 1080p high definition projector that I was looking at buying. However, since the Dell was only about $600 and I already had it, I think it is a pretty good option. Plus, it works great with my Media Center.