I was excited about the e-Reader add-on for the GBA when it first came out, because it had a ton of potential. It still does, but it's barely been used by Nintendo themselves (Clu Clu Land or Urban Champion are not what I'd call system-sellers), and not a single third-party developer (AFAIK) has taken advantage of it yet. Apart from the freebie Air Hockey card, it's been a waste so far.
Apparently not for long.
NES Super Mario Bros. 3 is coming out for the GBA in September as Super Mario Advance 4... and the following speaks for itself:
Nintendo's planning on releasing a series of e-Reader cards for Super Mario Advance 4 where players can transfer the data from e-Reader to the game (much like the way Pokemon Ruby/Sapphire handle the special Battle Card-e fights) to upload brand new levels and challenges. You'll need two GBAs (or a Game Boy player and a GBA) to take advantage of this feature.
SMB3 with new levels? Do I hear cash registers ringing?
EDIT: Oh yeah -- I've now played WarioWare, Inc. I may never sleep again...
(edited by vsp on 4.7.03 1557) "You may be wondering why I have been making so many references lately to Fox News. The reason is that it is now my cable news network of choice -- because if Iím going to watch the news and be lied to, I want it to be ridiculously obvious that I am being lied to." -- Center for an Informed America, Newsletter #34
Blaster Master, Golgo 13, Ninja Gaiden -- got to the end of them all and got toasted. Btw, Cerebus, Cliff Hanger had both Castle and Mamo clips intertwined. The majority is Castle, but there are some Mystery of Mamo clips in there.