Well, I am no dietician or doctor. All the sugar substitutes on the market have been approved as "generally safe" by the FDA when not taken in truckloads (like what they dose rats with).
Having said that, I tend to stay away from most of the substitutes because I get migraines from them (other than stevia derivatives), and digestive upset from most of them as well. That is not to say that you would have any problems with them.
Some substitutes work better for baking than others--some break down with only a little heating. If you like Sweet n' Low, than there shouldn't be a problem with you continuing it.
One thing I noticed with myself, and I am not sure if others noticed this as well, is that I tend to crave sweets the more that I have them. Sugar substitutes tend to compound this for me, so the more I have, the more I want. We also tend to sweeten things that are not nutritionally good for us--more filler than nutrition. Look at where you are using the sweetener and see if you could be putting those calories in better places.
Good luck, and if in doubt, try going without the substitutes for a week or two and see how you feel. That may be your best bet to see how it affects you!