What do you consider a "go-fast" boat? Around my lake it's 80 to 200+mph and there are a lot of them out here. On some early morning weekends we will see 300 bass-boats pass by our house at 70+ mph in under 20 minutes
On our Tomcat we prefer 17 to 22 mph for cruising. We have found that we experience much the same viewing at 17-22 mph as we do at 7mph, except for the fact we are tripling our viewing area in the same time period, and the ride is better. Unlike our previous open boats, we can also listen to music and have an 'inside-voice' conversation while on-plane. Our favorite 'motus operandi' is to cruise around at 20 mph on open water and 'same-old' stretches of water, and then slow to 5 or 6 mph to check out interesting coves, animal life, boats, boat-yards etc..
Another thing I like about the Tomcat is that when optimally trimmed around 20 mph, my maximum range is close to 300 miles, and at 5-6 mph my max range doubles to almost 600 miles. I'm always a little concerned about taking on bad fuel, so being able to pick and choose where I buy my fuel, makes for better sleep.