I started racing less than 2 years ago. While I'm still a CAT 4, I've got the points to be a 3 and I race in 3/4 races sometimes and don't have any issues hanging. From my perspective, the fast guys in the 4's are on par with the fast guys in the 3's, there's just a lot more depth in the 3's. What I really like racing is the masters category. It's much smoother, more tactics, and I see less testosteron-fueled stupid stuff going on (ignoring the fact that bike racing in general is stupid and testoron-fueled). I've done a handful of crits with the P123's and I can hold on for dear life, but those races require a higher level of fitness from my perspective and I don't see many CAT 3's making an impact in those races.