In all my classes, I try very hard to give students live feedback either when I grade them or when I am simply walking around watching them struggle with a problem. Although programming is a process of trial and error, certain errors can cause a lot of frustration and be a waste of time. Often, timely feedback can save a student time or illustrate a point.
One very important piece of timely feedback, which many times has been both instructive and helped the student solve their own problem, is the insistence on using rules of good style. Often, the problem is that the student is simply typing stuff up and trying to see if it works...having learned that things like whitespace, using meaningful names, declaring variables at the latest possible place, using emacs to automatically space things, watching all warnings etc. are not crucial to the program running correctly, students often postpone this as a final step to be done for grades alone. However, these practices will very often help the student find their problem. Often, students do not believe this, even when they are warned ahead of time. Forcing the student to use good style before giving them any further feedback often helps them find their own problem.
In our current system, we give very little specific feedback. One disadvantage of the electronic turnin is that students merely see a grade, not a report of why they got their grade. Hence simple mistakes or misunderstandings can persist and cause damage to a student's grade and hurt their potential for understanding. It is understandable that not all TAs are able to give specific and timely feedback on a student's coding or other lab work. However, the process can be simplified so that it is easier for even the marginally competent TA to give some feedback.