Is MSc the way to go?
Many M.Sc degrees in the US are not research oriented (try Canada, they seem to be more common here), and you should be wary of this. If you want to gain experience in research to see "if it is for you" then you need to find a thesis bases Masters, and not a course based one. A good sanity check to see if your potential Masters program will involve real research is to see who is paying who. If you are paying them, then this is not where you want to be. If they are paying you, then it is much more likely that you are in a research based masters.

In general, a Master's degree is a good way to test the waters. It is also a good way to shore up on any knowledge you might lack after being out of university for 7 years, and make sure you have all the necessary foundations (sometimes Information Systems degrees don't teach these). If you change schools between your M.Sc and Ph.D it also offers you a chance to work with more people and if you don't change schools you can often fast-track before graduationg as if you had been in a Ph.D program all along.

However, getting an M.Sc degree does have potential downsides:


it can take longer to finish the whole process (B.Sc + M.Sc + Ph.D tends to be longer than just B.Sc + Ph.D)
Ph.D programs tend to have more stringent requirements for applicants that already have a Masters degree.
Some funding opportunities (such as NSF) might end up unachievable.