They are considered "difficult" because if you aren't seasoned, by the time you realize something is wrong they are already dead. Other corals are a little more forgiving and give you more time to correct the problem.
They are also vulnerable to a pest that is extremely difficult to eradicate. Acro Eating Flatworms (AEFW). Coral Dips will not keep them out because the dip doesn't kill the eggs. I got them a few years ago and had to rip an established reef apart. Pulled all the corals out and had to dip weekly for 12 weeks. I lost a bunch of big Acro colonies I had grown from frags. Years of work down the toilet.
But when things are going well they are not too difficult. Keep parameters stable and Quarantine all new additions before adding them to your tank.
I got into the hobby and jumped right into SPS keeping. I had quite a few losses along the way but you learn from them. Eventually you kind of develop a knack for it and nothing really prepares you for it. So if SPS is what you want, go for it. Starting out with softies or LPS doesn't really prepare you for SPS so you might as well jump in with both feet. Just do your homework and start out with the "easier" cheaper SPS first. It's also better to start out with aquacultured SPS. They are hardier and if they die you aren't putting a strain on the reefs.
Once you figure out how to keep them alive and growing, the next level is getting them to color up nicely. There are a lot of people who keep SPS, but only a small percentage of them are able to get to that colorful mature SPS reef that makes your jaw drop. So if someone tells you it's easy, or gives advice, ask for pics of their tank. ;). It takes years to get there and there are many potential pitfalls along the way.
Wes
