Good times, Caterkiller. Time Trial is the real single-player content of Mario Kart. You only play Grand Prix until everything's unlocked, but Time Trial is dozens of hours of fun. Over the long-term, that's always the mode I spend the most time with.
I've only had MK7 for 10 days, mind you, so there's still a long way. As such, the only time I've logged that I feel might hang with this company is 02:29:503 on WII Maple Treeway. You've probably got me beat there, but hey, that's 5 seconds quicker than the best Nintendo Staff Ghost, so I was happy.
You've given me stuff to work on, though. My times on Daisy Hills and DK Jungle are both just 2 seconds behind yours - it's on!