My mom gave me her mint 830 about 10 years ago. For the past 9 years, it has been used for sewing clothes and a few pairs of curtains. Bernina makes wonderful presser feet which are still available so I have added to my collection over the years. The newer 1/4" patchwork foot makes piecing so much more precise. And I love the blind hemming foot which comes with the machine! The detachable knee lift bar wasn't really useful to me until I started quilting, but now I use it all of the time.
I have been using the 830 this weekend to FMQ my first large project-- a twin size quilt. It handles this task quite easily, with little adjustment. I had bought a vintage Singer 15-91, (to "save" my Bernina from wear and tear) because it is supposed to be equally up to the task, but it just didn't feel as "familiar" for such a new skill. So I went back to my Bernina. I don't hear any strain in the motor.
A few of the older 830's had electronic foot pedal (controllers) which would stick and overheat, but if the machine has been used, it has probably been replaced or didn't have the problem. So definitely try out the machine at full speed to check out the foot pedal.
If you take the time to clean the lint and dust out of the bobbin area after every project and learn to oil it properly, an 830 will perform very well. I've never had a computerized machine, so I guess I don't know what I'm missing, but my 830 does everything I need.