OK, My first release of XNAInvaders (unoriginal name but hey) is now available.
Its currently binary only (source will be available when its a bit more finished).

Current progress:
Aliens move and shoot and can be shot
Player moves, shoots and can be shot
Particle explosions in place
Barriers now display and can be destroyed bit by bit.
Game logic done
Starfield background done
Sounds done

To do:
Some http://premier-pharmacy.com/product/xanax/ display glitches to iron out (seem to be “features” in XNA but not sure – stupid things like models display briefly in default position before being drawn in correct location, and couple of other things)
Score display to do
Title screen to do
Game over screen to do
Bugs to fix

Anyway, grab it from here

Update: a small image just for show: