Okay, TeX isn't perfect. It has a few drawbacks, the foremost of which is that it's difficult to learn. TeX's learning curve isn't as vertical as, say,
that of FrameMaker, but it can take a while to pick up. Of course,
if you're familiar with a markup language like HTML, then
things are a bit easier.
TeX's graphics support leaves a lot to be desired. Anyone who has used a WYSIWYG application under Windows or the Mac OS knows how easy it is to insert and manipulate graphics. TeX lacks this simplicity. You generally have to
specify the image's height, width and position on the page. This can be tricky and takes a lot of work.
For all its power and speed, TeX demands a bit of knowledge from is user. You have to know some basic typesetting terminology and have to become familiar with some TeXspecific nomenclature. This includes terms like "badness," "boxes and glue," and "control sequence." Knowing what these terms mean will come in handy when reading a TeX error log.
TeX isn't a WYSIWYG application. You have to typeset your TeX file in order to see if you've made a mistake somewhere. From there, you either have to print the DVI file or view it in a DVI viewer. This can become a bit of a chore after a while. Some TeX systems (notably Textures for the Mac) can dynamically update the output, allowing you to see your changes as you make them.
LaTeX
While TeX is fairly difficult to learn, LaTeX makes things easier.
LaTeX is a set of macros that works on top of TeX. LaTeX makes it easier
to add graphics, build tables, include headers, footers, marginal notes and tables of contents, and more. Whereas TeX often requires a sequence of
commands, LaTeX can do the job with just one or two. On top of that, LaTeX comes
with several pre-defined document layouts (letter, book, report, and
article). The overall look of each page is set, although you can
change it with a little tweaking.
LaTeX is the fastest way I can think of for beginners to start using software. Still, some hardcore TeX gurus that I know sneer at LaTeX; they say it's "too touchy-feely!"