They are thicker jackets with a soft fleece lining and an outer technical fabric shell, with the two layers bonded together. The outer shell will give you SOME wind/rain resistance while maintaining better breathability than a hard shell like Gore-Tex. I have one, but it doesn't get used until temps are well down into the mid 40s or lower.

Everyone is a bit different, I can generally deal with temps down to low 50s/high 40s with nothing more than a long sleeve jersey. I don't think of tights until it is in the 40s, and if it is warm enough for shorts, I've never used knee warmers. What is important is learning how to layer, and working out what works for you. I get laughed at, because once it hits 80, I am generally in a sleeveless jersey, but I am not heat tolerant. OTOH, we're down to 60s nearing the evening here, where I am still in short sleeves and shorts, others are already into multiple upper layers, long gloves and long pants.

As [MENTION=4588]Machka[/MENTION] says, when it comes to jackets, cycling specific is well worth it.