I think it depends I have done two law placements as I am doing a 4 year course at Brunel.
The first was at a criminal firm although we got to travel to crown court and prison, most of it was colating defence chronologies.
The second was at a city firm. The work was varied and kept me busy, although it was unpaid. I did stuff like writing letters to clients, other solicitors, estate agencies. I drafted a decree nisi, proof read various employment contracts and more.
I was involved with alot, because it was a small firm dealing with civil cases.
However, I must say you only get good experience if you spend more than a month at a firm.