A friend of mine and I bought the Neo Geo Pocket Color the Christmas after it first came out - with some online Kay-Bee coupons we each got an NGPC for the sweet price of $55. We ended up getting a few games for it (it was kinda sad, we were the only two people who played it), but by far the one we played the most was Cardfighter's Clash. I got the Capcom version, he got the SNK version. I put at least 90 hours into the game, it was so much fun. It was definitely broken, though, due to the ranked system - once you got a few of the really rare cards, all strategy went out the window and it just became a game of "see who pulls out Mech Akuma first."
I picked up the DS version the other day but I haven't started playing it yet other than giving it a quick look-see. I want to finish Super Robot Taisen: Original Generation for the second time before I start anything new (I finished the Ryusei path and now I started over on the Kyosuke path). I hope that even if it's broken, it'll be fun. I'm happy to support SNK Playmore, anyway...they're putting out stuff like Metal Slug Anthology and the Neo Geo Collections (even if those are Japan only) which are truly gaming treasures.