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jstill made a good point in general:
of course you should play exploitable because you should only play in games where players are so weak that you can exploit them.
so the use of nash equilibria at the moment are very limited (ignoring that its to hard to calculate anyways today)
but there is definitly some attraction in the idea that you will make profit no matter how the opponent plays. especially if you are in situations where players are considered quite good but you don't have specific informations on them. or in games where players are really really good.
thats also why the SAGE system is quite popular. especially in low stack situations where you are not able to gather enough information about your opponents it is extremly useful to make sure you have at least a small if not bigger edge...
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Just to demonstrate your last point:
http://pokerai.org/pj2/images/stories/optVsExp.png
This is simple SS push/fold situation, you are on the small blind. You can see the EV for given push strategies - the different graphs represent different push strategies (optimal, push with top 8%, top 12% and so on). The Y axis is your EV and the X-axis is the call ranges (top X% of all hands) of your opponent.
Lessons learned? If you are against unknown, or very loose opponent it make sense to play optimal. If you are against tight opponent however, it make sense that you also play more tight than optimal, and in this case you can make upto factor 5 more profits (of course if you err on your reading, you will also loose quite some).