Llano should be great for HTPC setup and normal office work, internet browsing and those general use. Real world power consumption should also less than Phenom/Athlon + cheap discrete, measurable but not highly significant.

Llano performance also scales better with higher DDR3 speeds compare to cheap Athlon II which hardly benefit higher DDR3 speeds.

You may get cheaper build cost with older Athlon/Sempron AM3 but cheap motherboards also have outdated and limited features. Most cheaper/older AM3 mobos does not have SATA3 or USB3.0. Even built-in HD4290 (890GX) has lower performance than HD6530D in A6-series. Gaming at low resolution... Can't get any wrong with Llano.

Let say we're comparing Athlon/Sempron based AM3 with built in graphics HD4290 (890GX) vs cheapest Llano A4 with built in graphics HD6410D, the latter is like 5-times better GPU performance than the former. At non-overclocked setting, AM3 Athlon II probably max out at ddr3-1333 or ddr3-1600 while Llano can still benefit ddr3-1866 greatly.