That is one school of thought. I always prepaid my mortgage to the max possible and thought of the interest savings as returns (and ignored the obvious opportunity costs). Effectively you are getting 2.14% per annum after tax with no exposure to risks. To do this with an investment product in the current climate necessitates taking on loads of risk. The real difficulty is that paying the mortgage down early is really, really fucking dull (ditto making AVCs into the pension). The temptation to spunk the extra payments on holidays or toys or high yielding and risky investing is very strong. However, we now have no mortgage and I will have 2 full pensions (I Aussie and I UK) by the time I pack it in.
I likez da dull sometimes