Nevertheless, I think the time for quad-core is here finally in 2010. Not because it is necessary to have one but because there is no reason not to have one. A cheapest quad starts at below $100 and for $200 you can get one of the best performing quads.
I agree with lopri on this one. Today the price differential between a Quad Core processor is very low in the context of the overall system cost ($80-100). However, it provides that extra smoothness when running multiple tasks (especially if you plan to get an SSD, then you'd want a fast processor to let it all out

)
I even thought in the days of Q6600, it was worth it to pay $140 over E6400 or even E8400 for 2 more cores. A friend of mine purchased his E6400 in summer of 2008, while I upgraded to a Q6600. Now his is seeing 100% cpu utilization by running Linux and Windows in virtualization mode, despite having overclocked his processor to 2.66ghz. He now wants to upgrade to a quad core. Unfortunately the Q9550 is >$200. So he would have been better off getting a Q6600 way back and overclocking it, because the cost to upgrade on S775 is even more now than the price differential was back then.
So now, there is little reason to NOT get a quad core for an extra $80 if you keep the system for at least 2 years, that's just $40 a year...I mean come on!
Eventually more and more games will take advantage of multi-cores
http://www.pcgameshardware.com/aid,698761/Dragon-Age-Origins-CPU-benchmarks-75-percent-boost-for-quad-cores/Practice/
E6600 2.4ghz (65nm dual core) = 18 min / 28 average
E8400 3.6ghz (45nm dual core) = 28 min / 44 average
Q6600 2.4ghz (65nm quad core) = 31 min / 50 average
Core i5 750 2.66ghz (45nm quad core) = 44 min / 70 average
Q6600 3.6ghz (65nm quad core) = 46 min / 72 average
Core i7 920 3.5ghz (45nm quad core) = 57 min / 90 average