I've got one and use it quite a bit.
Pro's:
$25 coupons that you can use to buy gun related "stuff". (I use mine primarily for powder/primers, etc.)
I don't feel guilty about my shooting habits because I'm just using "points" to buy guns, scopes, powder, primers, etc.
Cons:
Gander's prices for alot of gun related stuff is higher than it should be.
Their website SUCKS if you like to use quicken and have it pull down your transactions.
I used to travel alot for work so it worked out well in that I used Gander's card for work expenses and it added up fast. (2k a week when I was on the road equaled about $75 a month in gander bucks)
The main reason I got their card was that I was looking for a Leupod 4.5-14 VXIII scope and Gander had them as cheap as anywhere I could find on the internet. I was ready to plunk down my cash and they offered me 10% off if I signed up . . .what was a good deal became a screaming deal. (I think I paid $430 OTD)
FWIW.