If you go for everything gold, it's harder then GT4 mainly because of Vettel and Grand Tour Eiger time trail (all much harder then the DM34 from EU version, the US version hard a harder time for DM34 but the SLR was also better tuned, so I'm not sure how much harder it was in the US version).
Still there's a lot less things to do in the game, then if GT4 (but not as few as in GT3, because of the Special Events, and then with the Seasonal Events staying forever it will end up more massive then GT4 someday... but for that we need PSN up again...).
"Ladies and gentleman, boys and girls, dying times here!" My GT4/TT Album: http://s97.photobucket.com/albums/l227/Han_the_Dragon/
As hard as you choose to make it, just like the rest of the series. There are only a handful of events you can't brute force with overpowered cars if you want and The AI is as stupid as every other GT game. Countering that, some of the events are among the most challenging in the series and racing humans is always amusing... once PSN comes back
Your effort to remain what you are is what limits you
2% of the population who own Gran Turismo 5 got the Platinum legit, while the other 3% are phonies that used hacking tools like Jail Breaker to unlock all the Trophies at once or just unlocked the hardest Trophy "Gold Standard". Most people who got the GT5 Platinum without cheating devices used a racing wheel but, can be done with a DS3 controller, which will take more skill and time. Gran Turismo 5 is the fourth hardest PS3 disc game to Platinum overall when done legitimately.
Lets say I am not going for the trophies this time and I just want to play it casual... Gran turismo 2 and 3 were excellent a little frustrating while getting some of the licenses but they were good... gran turismo 4 was extremely frustrating while everytime I made the slightest crash the screen just trembled and almost all cars were hard to control.. is GT5 like GT4 in theses aspects or it is like the other ones?
I don't find the cars hard to control, but I ddn't in any of the others, either.
You'll be happy to know you don't ever actually have to do the license tests if you don't want. There is a leveling system to unlock cars and races, and you will hear complaints of grinding, but I've never had to and there are several others that never have, either. Once PSN is up and the Seasonals are available it's like butter. I started a new game in the couple weeks before PSN went down....started with the FF seasonal in a used Civic, bought cars and did the other races, and by the end I went from Lv0 to Lv18 and had close to a half million and the cars i had to buy for the races.