Pros: On average, faster speeds; Adaptive voltage; z87 Chipset; AVX2
Cons: Voltages needed while overclocking wildy varies; Steeper OC learning curve; Adaptive Voltage; Hot
I'm going to put a summary here and put the in depth stuff in the link later on. Haswell IS on average, faster than Ivy or Sandy Bridge once you factor in the IPC improvements. I assume you're overclocking. The results vary a lot as the amount of voltage required at a clock varies a lot. It is truly a lottery more than ever with this one. Haswell can tolerate a bit higher temps than older chips but they run much hotter as a general rule. There is a problem with the CPU (the glue used inside) that may be fixed by a proper delidding. Also not that Linpack is a stress test for Haswell using Avx2 instruction set, blowing up the temps way above even other stress tests.
Adaptive voltage allows the CPU to sip power when not under load. This is good for longevity and power savings but comes at a price. If you do synthetic stress test under adaptive your voltage will implode. It takes much more to learn how to overclock this CPU well, so head down to my guide link below if you're interested. Some people just tried to tweak vcore and multiplier and raged in frustration. Don't be that guy.
In terms of price? Ehh. It's ok. The price isn't really higher now than when Ivy first came out but that doesn't mean you can't get an Ivy or even a Sandy for secondhand on the cheap, but you miss out on z87 chipset.
Below is a selection Q&A from my Haswell Overclocking Guide.
If you want to learn how to overclock Haswell, my guide has you covered. It also contains a Google Doc with all the Overclock.net members' OC settings charted.