You are mostly on-target here. I would argue that some great AMD options are available under $100. They are overclockable (unlike the Celeron/Pentium options) and are good alternatives. Cases could be made for either.
If you do not have a MC around, there is no better CPU between $150-200 than the X6. if you do have a MC, or get a good deal elsewhere, the i5 is better.
Yeah, but that will only take you so high... Previous $100 CPUs were exciting because of HOW much overclocking you could get, even on a stock cooler and with no additional overvolting. The Athlon II X2-X4 (AM3, not FM1) already come clocked high at 3.0-3.4GHz, and the highest they'll go on a stock cooler on stock voltage is 3.4-3.6GHz. You're gaining very little, and by then you'll barely be surpassing the Intel counterparts in some areas. You'd also have a less efficient processor, and because Bulldozer consumes so much power it's not advisable to get a cheap 3+1 phase motherboard for something like an FX-6100 in the future. Stock, a system with an FX-6100 will consume 50% more power than one with an i5-2400 or i5-2500K, which limits upgrade-ability.
I do agree on the X6 1055T in particular. For $150 you're getting a chip that at the same clocks as an i5 competes with it in multi-threaded workloads for a $40 lower price. Power consumption is obviously higher, though you should be able to get 3.5GHz on the stock cooler on stock voltage. Very few people have a MicroCenter near them, but if you have one near for $150 an i5-2400 is an obvious choice. You can easily get 3.8GHz out of it with the stock cooler and have a cool and efficient system.
Depends on that you're doing with you cpu. For most users I would advice against getting a dual core i3 over the quad core Phenom II X4 at this point, unless they specifically only or mainly need strong single thread performance.
EDIT: in the $ 100- $ 150 segment I'd also say the Llano A8-3xxx is the better choice unless you use a discrete GPU. (which few do in that segment)
I'd disagree. The Phenom II X4 955/965 is a bit faster than the Core i3-2120 in most multi-threaded applications, but in single-threaded it gets trashed. They don't have a lot of headroom on stock cooling either; having to spend $30 on an air cooler kinda makes the value go away. Most of them reach 3.6GHz on the stock cooler, and by then they'd widen the gap a bit in multi-threaded tasks while still being hugely behind in single-threaded and mildly multi-threaded while consuming a lot more power.
Llano is great, but for enthusiasts looking for bang-for-buck the Athlon II X4 631 and a dedicated graphics card is a better choice.