There are quite a few people that I have already heard giving this a sub-par rating, but I couldn't disagree more. I think that this card is an auto-include in any rogue deck that can pick up a level-1 upgrade such as "Skids" O'Toole, Wendy Adams or Jenny Barnes.
If you are going to swap out a single card (ever) this has already paid for itself. You can put off paying for it until you are going to want to swap things out, but honestly there should always be considerations of swaps in decks after you start playing it. No one's deck and design comes out perfect. Decks start out with certain themes and elements and should always find tweaks and personal preferences.
As we are playing, new packs come out all the time. With those new packs come other level-0 cards that you will most likely consider. And when you can swap them in for free with your current deck on the fly with those releases and become much easier to get those new shiny toys interacting with the cards you have been building around.
So far, it has already saved me 4 experience. Would all of those been done if they weren't for free; no (perhaps 1 or 2). It lets you be "adaptable" and improve yourself. Challenge your deck after every play through and every pack release. I think this is amazing. And paired with Charisma coming out in the new pack, I will likely use Adaptable again to build some additional allies themed into the deck after this purchase so that I can get a nice array of different characters for my Jenny Barnes deck and build on a nice new style of play. So, while others are seeing this as mediocre, I wanted to put my opinion out there. I think this card is amazing.