With the new Sandy Bridge cpus, it essentially obsoletes the older Intel i3/i5/i7 since the new Sandy Bridge cpus are faster than the older (fastest) i7. The only drawback of the Sandy Bridge cpus is that it requires a new type of socket, thus, the upgrade path will require a new system or at least a new motherboard. Full review from Tom's Hardware can be found here.
There are other Sandy Bridge cpus out there that are faster than the i5-2400 but frankly, they're simply there for bragging rights as this cpu provides enough performance for any task including gaming and is the best value for the money.
Specs: 32nm, Quad-core 3.1GHz, Intel HD Graphics 2000, 95 watt TDP, Dual-channel DDR3 memory support, socket LGA1155
i have Intel Core i5-2500K in my PC, it running smoothly, fast yet with very affordable price
Hey, no need for insults, you may simply post some stats and prove me wrong. And while I may be a bit overzealous on the Sandy Bridge processors, in overall cost to performance-wise they're a better investment right now. Here's a direct quote from the Anandtech review.
"Unless you're running a lot of heavily threaded applications, I would recommend a Core i7-2600K over even a Core i7-980X. While six cores are nice, you're better off pocketing the difference in cost and enjoying nearly the same performance across the board (if not better in many cases)."