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