Turbo Boost is available on both 2nd and 3rd gen Core i5 CPUs.
The general advantages of Ivy Bridge over Sandy Bridge are:
1. The Intel HD 4000 integrated graphic core represents the single most significant difference. It provides roughly a 40% performance boost in games over the older Intel HD 3000 graphic core. However, people who play games tends to install a graphic card, thus bypassing the Intel HD 4000.
2. The Intel HD 4000 offers better Quick Sync results for video encoding vs. the older HD 3000. However, if you do not encode video using the H.264, VC-1 or MPEG2 codecs and a Quick Sync capable video encoding program, then this benefit does not mean anything to you.
3. On average 5% better performance. An Ivy Bridge CPU clocked at 3.3GHz would basically be equivalent to a Sandy Bridge CPU clocked at 3.465GHz.
4. Ivy Bridge have lower power consumption, about 15w - 20w less power consumption when the CPU is operating at 100%.
5. Ivy Bridge CPU supports the new PCI-e 3.0 slot which has more bandwidth. However, current PCI-e 3.0 graphic cards have no problems running in a PCI-e 2.0 slot. It will probably take another 2 years for a PCI-e 3.0 card to be limited by a PCI-e 2.0 slot, and that would only apply to the high end PCI-e 3.0 graphic cards ($500+).
The main complaint about Ivy Bridge CPUs is that they get pretty hot when overclocked. The recommended OC for IB CPUs is about 4.2GHz to 4.5GHz. SB CPUs can generally overclock up to about 4.8GHz.
Don't forget that a IB CPU is on average about 5% more powerful than a SB CPU. Therefore, an IB CPU OC'ed to 4.5GHz will be equal to a SB CPU OC'ed to 4.725GHz.