I have been on the fence on if I would buy this game, but have not.
I finally put my finger on why.
I feel like Thunderstone Advance is just a fix for the original Thunderstone. Why should I have to buy a game twice to get a good version?
To be honest I felt much the same, but it is worth the upgrade. I suppose the alternative would have been for AEG to never have bother improving the game. I sold off all my old cards and now just have the advanced sets. One of my favourite games.