In civil matters, there are advantages to using a jury. The major advantage is that the public as a whole is more likely to feel that justice is being served. If civil cases were only tried by judges, people might feel that the legal system was not responsive to the common person. This might end up causing problems as our system came to feel less legitimate to a large number of people.
However, there are definitely issues associated with trial by jury in civil cases. One of the most important issues is the fact that juries can be prone to be somewhat biased. They might feel a sense of animosity towards large corporations that seem impersonal and excessively powerful. They may also award excessive damages, particularly against such large companies. This is something that many people have worried about in our current system and jury-awarded damages are sometimes drastically reduced on appeal.
One final problem is that jury trials can take longer and therefore be more costly. The lack of expertise on the part of the jury makes for longer trials. Therefore, non-jury trials would likely be more efficient, but there might be some reduction in perceived legitimacy of the system.