Overall the film was pretty entertaining. There's an odd side plot involving Burton's character running into his old schoolmaster, who's now a drunk and a private in the Australian army. I agree with several reviewers of the film that this subplot is rather awkward and should have been re-written or cut out, but aside from this one quibble, the film is quite enjoyable. James Mason plays Rommel as if he's born to the role (and he was Rommel in The Desert Fox, the movie that preceded this one), and Burton is also quite good, as are the rogues gallery of Australian "desert rats" in the movie.
There are a number of action sequences, some of which were entirely shot for the film and some made up of new footage spliced together with war documentary footage, a common practice in these old war films. The middle third of the film is especially good, detailing all the night raids and missions carried out by the Rats against the Germans - blowing up supply dumps, knifing sentries, and causing general havoc within the German lines. I think the film also does a good job of showing the incredibly harsh conditions of the Tobruk defenders, men who're literally living in holes cut out of the hard desert earth for months on end.
If you get a chance, find this movie and check it out. If you're a classic war film buff, I don't think you'll be disappointed. Here's the trailer for the film: