I have had this for a week, and have used it every day. Day 1 for 2 hours at 1.5MPH, same the next day, then 3 hours at 1.5, then 3 hours at 2.0 for the next 2 days. I thought it would take longer to get use to typing and mousing. I'm not as proficient as I am at my sitting desk, but very close. I also talk on the phone while on it and the treadmill is quiet enough that the other person cannot hear it. The only thing I'm not able to do is write very well. I spend an hour on it before lunch, then 2 hours in the afternoon. It breaks up the sitting nicely. I might do more than 3 hours eventually, but others in my office are using it some too to see if they like it. So far it's been a huge hit. The automatic height adjustment on the desk was critical because I knew others would want to use it. It works very well. Also the desk top surface is much larger than I expected it to be. I guess true to life vs. the picture, but I still expected it to be smaller. I find that my monitor (on the arm that I bought separately) shakes a little - not enough to be a problem, but enough to be slightly annoying. I'm going to find a different solution where the monitor is not attached to the desk. At any rate, I find that I get involved in my work and suddenly I've walked 6 miles. Wow. I got this for my back so I wouldn't be sitting 10 hours a day, but the added plus of calorie burn is a great additional benefit. I still do my hour on the treadmill at home in the morning before I come to the office. So far the time on the desk treadmill hasn't been "too much". I just love this.