For me, the thing I hate the most is vacuuming out the car. I am the guy who ALWAYS (not sometimes, but ALWAYS!) finds that french fry, napkin, gas receipt, etc. that gets sucked in and clogs up the vacuum so that you get really poor suction until you turn it off, pull out whatever it is that got sucked up from the crevasses under the seats, between the console & the seat, etc.
I used to hate doing the inside of the windshields, as most of you have mentioned - and then I found this thing:
Glass Master
This thing has helped my sanity on cleaning the inside of my Ford Mustang (long dash, and I couldn't reach down to the bottom of it where it joins the dash & the glass) and on my mom's Toyota Corolla (another long, sloping windshield which I couldn't reach down towards the bottom at the dash & glass). It's not PERFECT, but when it comes to getting the glass down towards the bottom of the windshield, this tool is the go-to gadget for doing the inside glass.
Claying used to be a hate for me because it just seemed to take SOOO long to do a car - and then I discovered I wasn't doing it right (I was letting the clay dry out, not using enough detailing spray - fortunately I learned that lesson on my own beater car before I started doing it for the occasional money payout). Now, I find claying to be cool, because I get to go, "WOW!!! There was a TON of contaminant on the paint! And *I* got it off the car!"