Life-Tech interview questions

I contacted an employee of the company through Linked IN. The employee had posted a job description (opening in his group). I spoke to the would-be manager on the phone (approx 35 min interview), and received a good impression about the company and the position. I was contacted within 3 days by an HR person. The HR phone interview did not go as well as the first interview went. I was continuously cut-off by the HR person who seemed keen on just moving the interview off the todo-list. I didn't hear anything for almost 3 weeks. Then a call came letting me know I would be invited for an in-person interview, and I will be contacted by a coordinator to arrange the plans. The coordinator was very competent, and plans went pretty smoothly. In the interview, I was asked to prepare a presentation for the group, and then speak to each panelist for approx. 20 minutes each (separately). It was a long day, but went pretty well. The offer was received about a week after the interview. The background check and the drug-test was a bit off-putting. I've never had to do this for a job before, and I have worked for large corporations.