We have the Baby Safe Sleeper too, and we also love it so far.
OP, I will try and sum up our experiences as quickly as possible, but I apologise if this rambles... We also have far away family, and are planning an abroad holiday in the summer, so the Sleeper was our top choice, for the reasons you have.
It goes over two seats in the back, and clips at either end to the seatbelts. The carry handle forms a roll cage so it can't tip over in case of sudden braking or front/rear impact.
It is a bit fiddly to fit the clips onto the seatbelts, but you only have to do that once. It also takes about a minute longer to clip it in each time you use the car. The way we see it though, is that everything takes longer with a newborn, so a minute extra getting into the car is neither here nor there
It fits on the B Smart/Vigour chassis, which is so easy to manouver (sp?) and put up and down, so we're really happy with that too!
The other thing is that it only lasts until 6mths/10kg, so I'm already starting to think about the next seat up. It only delays getting a rear facing seat - it doesn't replace it. I might get a Britax First Class, which will rear face until DD is big enough to forward face, or might enough look into a rearfacing til 4 seat. But that's a conversation for another thread.
Hope that helps. Good luck with making a decision. Holler if you have any other questions!