Imo, over time, it improves your speed of calculation and intuition.
But only if you understand certain positional concepts.
Bullet does very little for your game, but 3/4/5 minute games put pressure on you and imo they FORCE you to think faster.
Well that's how it works for me, anyway.
I've also watched loads of Kingscrusher's videos on youtube, and they've really helped my understanding of what plays are important and when they're important.
"Timing" of plans is everything, and since (imo) the timing of plans is pronounced in blitz (and so you improve on this when playing lots of blitz games), when it comes to longer games, your thought process is automatically better, faster, and more accurate.