From what the developers say, there is some benefit in study(indicator) calculation when using a dual-core system. If your trading involves frequently calculating multiple complex studies, this may be worth the investment.
I have tried 1.9 on various PCs with 1 to 4 cores. I find the major benefit of a multicore system is encountered when more than one symbol or study is tracked at once. There is relatively little speed pickup when a single study is posted to single symbol, even for a relatively complex study.