I think there have some studies done for driving that suggest that people consider 30 minutes or under a reasonably short commute and anything much over that is considered "long".

For me at least that is true. For driving, I consider anything under 30 minutes to be close. A forty minute drive is psychologically different. Don't know why that is. Anyway, that's just for driving. For riding, my Winter commute is at least 10 minutes longer than my Summer one for various reasons and I consider it to be a significant difference.

So if you can cut 10 minutes off your commute, it's worth something. 5 minutes? Eh.

Personally, I don't think equipment changes alone are going to net you more than a few minutes. There is an X-factor though. Sometimes a change in equipment makes working harder more rewarding, or at least less uncomfortable. And other times just knowing that you dropped $200 or $2,000 on something in order to go faster, is enough for you to make damn sure you go faster.