I'm in Crystal River right now, and I can confirm that as of now, a lot of the restrictions regarding Three Sisters have not been put into place. That being said, there is apparently a new guy in charge at the Fish and Wildlife Service, and he has been quite trigger happy closing the springs to visitors. This morning, we arrived at Three Sisters well before 7 and were one of the first boats there, only to have them close the spring right after we got into the water. A lot of the captains are quite unhappy with this new policy. I'm really hoping that we'll be able to make it to Three Sisters tomorrow, as we haven't been able to make it there yet on this trip due to all of the closings.
With regards to strobes, I didn't bring mine and have been pretty happy about that decision. There is no flash photography allowed until one hour after sunrise, and honestly, in Kings Spring, the place where we saw by far the most manatees, the water is so murky that strobes would only add more backscatter. I suppose they might be worth it if you can actually make it to Three Sisters, but there's so much ambient light there it's almost unnecessary. More than likely, you'll just end up packing two heavy strobes that will only be of real benefit for a few shots. For the rest, you'll probably just have the manatee police yelling at you, regardless of how careful and responsible you are.
A final note: If you can't make it to Three Sisters, ask to go to House Spring. It's where we ended up this morning, and although it's very small, the water is even more clear than Three Sisters (so I've been told), and it stays less crowded.
Hope this helps!