(Response to liquidsnake718's generational shift comment)
For some users, such as myself, this shift must occur quicker than for others. (Further, as far as I am concerned, the jump will have occurred when these mainstream boards are stable and the "slightly better quality" have been released.) This is due to the following:
1. Cpu: Core 2 Duo e4xxx & e6xxx changed to Core 2 Duo e5xxx, e7xxx, & e8xxx. Further, quad cores were released. And, even further, now the core i7 & then i5. (In short, we have changed die sizes.)
2. For those of us with 6xx Nvidia chipset MBs for SLI capability, since Nvidia was the leader in graphics quality with their 8xxx era cards, we don't have a choice in upgrading. In short, our MBs are failing. (Time for a change to Intel boards and ATI graphics, especially with Nvidia's annoucement yesterday of their technological focus being not on 3D gaming.)
3. Ram has shifted from DDR2 to DDR3.
4. HD quality, power usage, and capacity greatly improving. (In my case, Seagate 320 GB 7.2k 7200.11 drives to WD ~1 TB Black drives.)
5. Video cards... no reason to get into specifics.
6. Rampant increase in power supply requirements for running SLI / Crossfire video cards. (The 500w PSUs I put in my systems were good for the initial graphic builds of 2 SLI'ed 8600 gts's during the 8800 gt's reign.)
I've always seen the pc market as having 5 tiers instead of the typical 3. (Lowest to highest in price)
1. Barebones systems for internet / office usage only.
2. Home Theatre / budget gaming pcs. (Yes, the Home Theatre ups costs, but the core components of the 2 systems are virtually identical.)
3. Mainstream gaming pcs. (Where I build my systems.)
4. Enthusiast gaming systems. (Still air cooled, but using the best or second best of most components.)
5. "Must have the best of everything."
As a frequently mentioned article on this site's forums analyzed, building a new mainstream system every few years (with minimal parts being transferred) and upgrading ram and video card once during the system's life has the best "cost to performance" ratio.
In that regard, once the lga 1156 boards and i5 750 have shown a reputation for quality (instead of just "being new and the best cost/performance"), they will be the perfect upgrade.
Prior to the i5, the higher end AMD Phenom 2's filled the role. But now, AMD has even more catch-up to do.