Autosave sucks because there simply is not enough information about the cars or the races before you buy them. When I started the game, I wanted to enter the Boxer competition, but I have no idea what a Boxer is. Horizontally opposed engine, whatever that is said the racing game newbie. There's so strategy guide out yet, and when I check for the race details all I get are a few choices and then "etc.." What is "etc.."? I have to guess now out of a list of probably 400 available cars as to what's a "Boxer", and then do it again as to what a "Roadster" is? At least GT3 gave me the list so I knew what to choose from.
Of course the Boxer race is just one example. Unless you're a car expert, many cars you try to buy have incomplete information, so you have NO idea if the car can be fitted with racing brakes, carry a wing, be NA tuned, or be able to hold a supercharger. Because of this it's just trial and error, and if I choose incorrectly, I just have to (at a minimum!) waste 10 minutes B-speccing something at 3x speed to get back exactly where I started from.
GT4's autosave is a design flaw in the game, just like "etc.." in race selection, the CPU's endless gas and extreme tire efficiency in B-spec mode, and the lack of detailed information in the car buying process.
I'm currently annoyed because I tried to bring my Camaro SS into the NA Sports Pro race just to find out it's not NA at 500ish HP because it has a supercharger on it, even though my garage told me it was NA and not Supercharged. I won the Camaro a while ago and it's stats were not fresh in my memory. Sure, no harm done, it was just another waste of time going back and forth (with autosave delays!) due to GT4's lack of information.
My other latest autosave fiasco involved finding a good car which gave me about 30-40 Aspec points for the Japanese championship. I don't want to blow through a race getting 3 aspec points but I can't afford trying out 20 combinations of cars trying to make it challenging but not impossible. If I had autosave, I wouldn't mind firing up a Civic, checking Aspec on the first race, restarting, upgrading to a Skyline, but not necessarily a highly tuned Skyline, etc.
This week, I'll be tearing apart my save game information and figuring out the right places to hex edit in order to add a trillion credits to my game. Sure, it's cheating, but I can already gain unlimited credits, 110k at a time, by B-speccing the Tuned Cup with a 700HP Skyline. At 27% completion I'm certain I have at least 1 million in wasted cars or wasted car upgrades in my garage. Properly tuned cars running in the right B-Spec races makes money a non issue but since that's just pure busywork I'll skip that step.