Most feather beds are very comfortable and will certainly increase your comfort.
Most feather beds rarely shed, you'll only see a feather or two a week.
You don't need professional cleaning for most feather beds, but it helps if you can afford it.
Some feather beds are portable but transporting them may not be all that practical since they're not like sleeping bags or cots.
Feather beds have come along way now with stitching that keeps the down in place. The down does not hurt when you roll it up as it doesn't poke through as much as the feather and down mix, or nearly as much as the older feather beds.
You can buy zipper, or velcro covers for feather beads for extra softness.
Many doctors are now saying high density foam beds to have benefits. Traditional mattresses do not give proper support to the back and neck.
You can buy feather beds at most well known dept. stores such as Sears, Macys, ect. You can also buy them on Amazon.com. Yes, you can buy cushion feather beds.
It will depend on each individual person as to whether a feather bed is better than a regular one or not. If you like soft beds with minimal support and are not allergic to feathers than feather bed may be best for you. If you require a firmer mattress or if you are allergic to feathers than it is not a better choice than a regular bed. Additionally a feather bed will hold more heat so in a warmer climate it may not be the best choice.
A poster bed is a bed that has four vertical columns at each corner. They are pretty sturdy and are rather traditional beds. They're not necessarily better than other beds though - it's a stylistic thing.
Any featherbed will work well in colder climates.
Yes you should fluff and shake the feather bed often to make sure that you keep it in the best shape as possible.