I bought this mainly for use when I travel but I also works great when you can't get to the gym.  Amazingly compact as I can easily fit it on my carry-on bag and go anywhere.  It's pretty cool that you can keep all the bands in the door loop and can quickly connect/disconnect the ones you need to do the exercise.  I also like the varied work-out from using weights.  One thing nice is that the resistance increases the further you pull the band, which helps when you are working through an injury as a lot of stress occurs at the beginning of the movement (bad with weights).  Even if you are pretty strong you can get a good workout using a combination of the bands but I will probably get one of the higher weight bands.