The Good: Weight, durability
The Bad: Confort for long rides
When you are searching for your next seat you may not pay too much atention to the I-Beam options because you can't choose the seatpost and seat independently, but don't see that as a disadvantage.
SDG making both the seat and post makes for a better integration and for a very light, yet strong and durable setup. Also, the setting up of the seat is extremely easy, and the adjustability is great.
Mine has sustained almost 2 years of riding, with your tipical crashes now and then, and the only thing I can complain is that the graphics are wearing off.
Confort wise, if you are into enduro or other similar type of riding, I would advise you to look to other SDG offering, as the I-Fly isn't the best seat for pedalling. But if your thing is Downhill or Freeride I would definately recommend it!