It was true for some time that AMD produced solid budget gaming platforms for significantly less money than Intel, that was true for the P2 X4/X6's, now that they have discontinued that line it is no longer true that AMD can claim that title anymore, by and large the FX chips are badly referenced priced. I would say that if the end user has an existing AM2/AM3 or 3+ setup then yes the FX is a very feasible upgrade path.
I didn't expressly call AMD chips crap, and if I gave the impression then I am sorry for that. This thread the OP wants to accertain the correct position on FX v Core I (sandybridge) and if we are going to lie about how good FX really is, then I would say we are being irresponsible. The hard simple truth is that FX is a good 2-3 generations behind Intel. If we are honest of where FX stands it is by and large on a par with Phenom 2 architecture which is old and antiquated now. I don't condone the position of telling a person to buy a P2 X6 1100T on the basis that you should never upgrade with old discontinued technology.
I don't appreciate the "fanboy" retorts, I used to be a AMD user but since Core2 there was no reason to go back, I buy on the basis of price/performance and right now Intel does that better regardless of just how badly they undercut the consumer. I have not alliegence to any manufacturer, I have used Asus, Gigabyte, Msi, Intel, Amd, Nvidia and ATI/AMD, corsair, Gskill, Kingston, Antec and coolermaster. I don't confine myself to myopic allegience to the cause. They "Avoid" tag associated with the FX line is derived from the experts of tech sites that live and breath benchmarks, you can go from PC Format, NAG, Tomshareware, Anandtech, HardCorp ..... and they are all giving the FX damning reviews.
Just to make the point on the FX bad reference pricing. In my country the FX 8150 goes for around R3300 while the i5 2500K sells at R2200 it is prudent to take the 2500K as it cost less and is more efficient, sure the 2500K is slower at highly threaded applications, for which I don't use. For everything else the R1000 was put towards a PSU and GPU cost. The 2600K goes for around R3400~ so the small added premium or R100~200 is neglible for the virtual domination the i7 has over the the 8150.