There are many new technologies, and they mainly make the TV a lot thinner.
Plasma & LCD flat panel displays (LCD comes in projection and flat panel!) are the type you can hang on a wall and are just a few inches thick.
Image compared to CRT: Not even close
The rear projection major players are CRT, LCD, and DLP. There is also the small player - LCoS.
Rear projection with LCD, DLP, and LCoS all use cabinets that are about 12-18 inches deep. The small form factor of the projectors inside the cabinets allows for a big screen without a lot of space being used. Very cool - but the image is sub-par compared to CRT rear projection.
CRT is still the gold standard for displays. It is better than plasma, and LCD flat panels. It is better than LCD, DLP, and LCoS rear projection sets. It not only provides a better image, but the cost of CRT is typically far less than the inferior image quality displays!
The biggest problems with CRT? Well, they are not as bright as other technologies which is typically not an issue. They also use very large, bulky cabinetry and heavy projectors inside. So, they aren't light, thin, and nearly as sleek as the new technologies.
But, they work - and they work really well for a really long time and at a fair price.
If you have a room that allows it, you can actually put a CRT rear projection TV into another room and just face the screen through into the room you are using - or build cabinetry around the TV to hide how deep and ugly the big CRT unit is.
If I had the space, I would definitely have gone with CRT for rear projection... I went with front projection though which is way more cool and fun though.