Okay, guys, so, after years of playing FPS and years of switching mice, I finally came out with more knowledge regarding sensitivities (and mice).

I will explain how I proceed to change my sensitivity, but first, what I will say is quite obvious but still, if you want to be consistent, if you want to feel very comfortable with your settings, try to stick with 1 sens/1 cfg for at least MONTHS. It's not a secret that those with the best aim play with the same mouse/cfg for YEARS (l1nkin, toxjq, strenx, k1llsen, stermy). If you always change this or that, if you keep switching mice, you will NEVER reach the "wow, it feels so smooth" feeling, you will NEVER be comfortable with your settings.
Personally if I change my sensitivity to about +/-6cm, I need AT LEAST 1 or 2 months to get used to it at 80-85%. If I change my enemymodel and/or my crosshair, I need AT LEAST 3-4 weeks to get used to it at 85%. Feeling very comfortable with your settings definitely takes TIME.

Okay, now, let's talk about sensitivities.
First of all, I will show you what is a GOOD sens, and what is a BAD sens, with 2 examples. This is what I consider to be a bad sens : 3.128, and what I consider to be a good sens : 3 (or even 3.2/3.1).
Often people came up with the conclusion that a sens with 3 digits after the point is more precise, and this is totally WRONG. It's basically just over complicating your sens. Sens 3.0 or 3.5 is way more simple, and clean.
This is how you will have to proceed with a 450dpi mouse :
- start at 0, then add +0.7
- sens 0.7 @ 450dpi is fucking low, so you might want to increase it then
- add +0.7, now you have sens 1.4
- might still be too slow, then
- add +0.7, there you have sens 2.1, finally something playable
- if it still feels a bit too slow for you, then add +0.7 again
- now you have sens 2.8, which is a perfect 30cm/360° (this is my current sensitivity btw)
If you're playing with mouseaccel, you might try :
- either sens 1.4 + cl_mouseaccel 0.05
- or sens 2.1 + mouseaccel 0.05 (and if you think that it's still not enough accel, then add +0.05 to your mouseaccel value, would be 0.1)

Now you will probably ask, "but why 0.7 and not 0.5 or 0.35 or 0.125?", it's very simple actually : at 450dpi, when you have a difference of 0.5 sens (probably 3-4cm on the mousepad), it's hardly noticable enough. Sens 0.7 gives you approximately 5-7cm, which starts to be a notable difference. Anything lower than 0.7 is just gimmick and unecessary.

Then if you're playing with 800dpi, start with sens 0.4. For example with my old kinzu, at 800dpi, I did :
- start at sens 0, then add +0.4
- too slow, then add +0.4
- now you have sens 0.8, still too slow then
- add +0.4, sens 1.2, okay now it feels quite good, but still a little bit too slow, then
- add +0.4, sens 1.6 : perfect. About ~32cm/360°.

Now, if you're a high dpi user, for example 3500dpi, then start at 0 and add +0.1 (sens 0.4 (0.1 x 4) is about 29cm/360°). For 2300dpi, start at 0 then add +0.2 (sens 1.0 ( 0.2 x 5 ) is about 16cm/360°).

That's it, I hope that this will be helpful to some people.

Best regard,
the one and only,
Heartlesss