By a strange twist of fate I am giving a small lecture/talk on Shmups at this years Screenplay festival in Nottingham (UK). I've got a short outline of what i'm going to try and cover and wondered if you guys could have a look and see if i'm missing anything vital.
The outline is below, and please note that Im looking for any other broad aspects I should touch rather than specifics :like, you havent mentioned pulstar etc

and of course shmups.com is gonna get a big plug!
History:
Arcade heritage: Space invaders - defender etc, different appeal to hardcore/casual
console/arcade comparisons
The formula: easy to play, hard to master. Established format but with opportunity for expression in gameplay and design
GAMEPLAY:
Playing to Score: A dying approach to gaming, repeat play, recorded replays (DVDs), community & strategy
Score systems: Chaining, Proximity, multipliers etc
Puzzle Elements: Ikaruga,Psyvariar,RSG
DESIGN:
Artistry: From traditional (1945-IBARA) to alternative (Guwange-Shikigami) to abstract (Asteroids-ABA/Psyvariar)
2D/3D: Still a haven for 2d design, but with increasing 3d elements
As Art: ABA games, Rez, Ikaruga (high)// Shiki, Cotton, Dangun (anime/toon)
DEVELOPMENT:
Production team sizes/techniques, still possible for indie development.