How many of you have splurged and spent the big bucks to upgrade their magazine springs to the chrome silicon steel type like these?  

http://www.brownells.com/aspx/NS/store/ProductDetail.aspx?p=20230&title=AR-15+MAGAZINE+SPRING

Do you think they are worth the hefty price?  

I wouldn't waste my money, or yours on them.

I bought 5 on the EE, not too much of an investment.
Then placed them into my "high-use" 30rnd mags.
It is just an experiment, and they have not failed once.
For the cost if it saves one FTF when my life is on the line
I think they are worth the small cost. I would not spend the
cash to replace the springs for all of my mags.

The 30 round springs can be purchased at a better price than you have listed.  CMMG has spring and new green follower for $7.95 and I have purchased them from the Computerguy on the EE for 4.50 a spring.  The price you have listed at Brownells for the 20rd springs is the best price I have noted.  

At $4.50 a spring its pretty good insurance, the choice will ultimately depend on what you use the mags for, competition and/or self-defense or merely plinking at the range.  It would also depend on the use your current mags have seen, new mags with the old type springs may not be worth the extra purchase.