I recommend using another option. The program is free but only for 50 converts. I found free versions that convert much faster and with better quality. To top it off it took 2 hours to convert 153 files and in the end it only let me convert 100 of them in two days. Many better options out there.
Sorry for the issues you had. Although there is a 50-file limit per 24 hours for our free service, there's no limit for any of our paid accounts. It sounds like the delay you had was with the upload of the files, and unfortunately we don't have any control over your internet's upload speeds. We can only convert files as quickly as they are uploaded to our site. If you had any quality issues, feel free to email our support team at support@zamzar.com and they'll be happy to help. Thanks, the Zamzar team.