That first year working 80-100 hours a week without a paycheck was my favorite part!
Then that 2nd, 3rd and 4th year of working 80 hours a week and drawing a 40 hour a week salary. Dealing with accountants that have no idea what they're doing. Firing that accountant and getting another one that doesn't know much more. Hiring people who work a month and quit, or hiring people that can't pass the drug test you told them they were going to get, or dealing with bad debt from the 2% of customers that don't pay, or....
But I wouldn't go back to working for someone else for all the tea in China.