Splenda has not had any reported problems, and it's actually been out for quite a while. I use it over Equal or Sweet N' Low, because those have tested side effects. So yes, it may even be safer than the other diet drinks.
Diet Rite isn't copied off anything else, but they are one of the few that have officially made the switch to Splenda (sucralose) from Equal (aspartame).
As long as you get your water in (at least 64 oz a day), you can have a couple of sodas. Just try not to let them take the place of water in your life.