Its an interesting subject. Should voting be considered a civic right or a civic responsibility? Does a politician elected under a compulsory voting system enjoy a greater sense of political legitimacy compared with one vote d in under the non-compulsory system.
Under mandatory voting systems, voters are allowed to offer a spoilt ballot if they wish, although personally I like NJs suggesting of a "None of the Above" category which could offer a real sense of voter disillusionment.
It is also interesting that under a compulsory system, voting is changed to the non-working days of the week, something else that may be seen as an improvement.
Fact is I think we have a problem in this country. Turnout in general elections suffered a major fall back in 1992 and is recovering slowly, if at all.
http://www.ukpolitical.info/Turnout45.htm
Average turnout in local elections is even worse, at around 40%, and then we had the recent PCC debacle, with a pathetic 15% only.
http://www.guardian.co.uk/news/datablog/2012/nov/16/uk-election-turnouts-historic
I certainly think we should be looking at ways of improving the turnout. Why not shift elections to the weekend, for example?