The reason they are so popular is that they are easy to install, easy to clean and maintain, very inexpensive, and come in a huge range of textures, patterns, and colors.
You will want to take some care with them; use a cutting board since scratches and chips from sharp knives will damage your countertop fairly easily. If you do get a scratch or chip call in a professional to repair it or you may be replacing your countertop.
Always use trivets since the countertop cannot take heat from hot pans and burns and scorches cannot be removed.
While solid core laminate is a little more expensive it is worth it. Since the color runs all the way through it small scratches won't be obvious and both your seams and edges will look better.
A design element I like to see when it comes to plastic laminate countertops is when people add a stone or tile edge material on them. If you are interested it is not hard to dress up your counters that way, you can have the manufacturer leave the countertop front edge open (just like the ends) and then you attach your edging choice after the countertop is installed.
One last thing I would like to mention is when it comes to backsplashes the post-formed backsplashes look so much better because it has a seamless look. So keep that in mind and think about purchasing your backsplash at the same time you get your plastic laminate countertops.
