It doesn't use Construct Sprites but handles its own rendering (technically: textured quads in the case of rotated bullets, point sprites when there's no rotation).
Haven't ran very scientific benchmarks, but it's pretty fast. Here's a test I did just now:
Over 20000 bullets on screen (a bit of a challenge for the player ), colliding with one object (player ship), still pushing over 60 FPS. (2.8ghz dual core, GF 9800 GT).
stare at this long enough and your screen will begin to wave
I can probably optimize it further, but there's still features to be added first. Anyway, performance is not the main catch here (Construct could easily push a few thousand Sprites -- more than enough for games) but the ability to script the patterns.