1)
Burying pressure treated 4X4 into concrete is how most fences in the North East are done. Yes, they'll rot--in many, many years. Rot will set in faster in the south where there's more heat and moisture for more of the year. If you look online you'll find all kinds of people swearing up and down that the new PT wood is crap (it's not) and rots in a week when buried, etc., but you don't need to over think it
2)
If your soil is hard/rocky/clay, like many, many people's is, digging the holes by hand is plain sucky. I dug several a month back and even a 10-12" diameter hole 30" down in clay soil is not fun at all. 1-2 hours of hard labor per hole. A fence could require a couple dozen holes or more. I know from experience in my yard if I were to build a fence I'd mark the holes and pay somebody to dig them for me. Look on craigslist and many people offer these services; a small bobcat with an auger attachment can do a hole in 5-10 minutes and do hole after hole. You may need a rest after each one.
3)
This: http://www.homedepot.com/h_d1/N-5yc...d=post+hole+digger&storeId=10051#.UCJpC_ZlTvY is relatively worthless in hard soil. Certainly you'll never put it into the hard, undisturbed soil and pull anything out, so all it ends up good for is pulling out the soft soil at the bottom of the hole that you already loosened with another tool (be it a very thin ended shovel or a metal bar, used to pick/grind away the dirt). In truth a shop vac is better in many cases for that: less work and quicker to pull the loose stuff out
4)
Pre-made fencing is fast and works fine on a flat yard. On a grade it looks worse, varying from ok to terrible. I have a neighbor who's in the midst of building a fence now on a grade and he's too lazy or too stupid to cut the bottom of the pre-made panels to match the grade, the result being not only a stepped look at the top (which looks bad but doesn't really affect function), but also at the bottom; he's got gaps almost a foot high at the bottom now. I'm hoping we get a strong enough wind to blow it over so that he is forced to start over and do it right.
5)
Also to others, concrete has no place in setting a fence properly. It causes the wood to rot faster and then is a PITA to fix.
Tell that to all the professionals who use it every day. Again, ground-contact rated PT wood, particularly in colder climates, is going to last for many years, whether set in concrete or not. Setting in compacted gravel makes it easier to replace the post but concrete is the hardest stuff there is and will lock it in best. The debate is like Ford vs Chevy; there are many on either side who swear their option is best. The simple truth is both work.
http://www.finehomebuilding.com/how-to/qa/preventing-fence-post-rot.aspx
http://www.finehomebuilding.com/how-to/articles/building-a-picket-fence.aspx?ac=ts&ra=fp