New and some Questions

Hmmm Im bored at work so ill take a stab at this question, hopefully others with more knowledge will chime in

Questions:
1. Do I need full body armor for XC and technical single tracks?
Full Body armor would be too cumbersome and hot for XC riding, Any extended climbing in body armor is gonna be very uncomfortable, If you ride within your skill level a helmet might be all you need. Although after a several thousand dollar dental bill from a fall I started wearing a mouth guard but I dont see many people wearing them. (edit full finger gloves have saved my hands and fingers)

2. is Full suspension or hard tail better for my riding?
Full suspension is the way to go imho,An effective rear suspension will give you more comfort, better descending, more traction on tech climbs

3. Are disc breaks worth it on my interest areas?
Yes, The stopping power of Disc brakes vs Rim brakes is crazy, A nice set of Hydraulic brakes will further improve braking (your hands will thank you)

4. How important is bike weight for mtb? Road bikers pay thousands to save 1kg on bike weight
Its a personal preference, My xc bike (specialized stump jumper) is aprox 28 lbs and Im happy with that weight, to get significantly lighter you are either going to have to pay big bucks or sacrifice strength. Find a bike you like and demo it at different spec levels to see if the extra cost for a lighter bike is worth it for you.

5. What are some of the top bikes (budget is not unlimited but pretty high) that would suit my area of interest and body/weight?
Id list a budget range, 2k 3k 8k ?

6. What are key differentiators between different bikes in same category (comfort or what)?
Not much, the biggest difference will be what type of rear suspension design they use, geometry, warranty, customer service

7. Is Carbon really stiffer and better than Alu for a mtb?
I dont know, don't have any CF on my bikes

8. What is the key difference between a full XC bike and a bike that is also a bit more than pure XC - (eg full mountain)??? [/U]
A more aggressive bike "all mountain" will generally have a greater amount of front and rear travel, id say a front fork with 130-160mm of travel up front and 5.5-6.5 inches in back is a good range, a slacker geometry and wider wheel base for better descending at the cost of climbing ability, stronger components (handlebars, stems, cranks, frame, wheels) to handle bigger hits usually at the cost of weight.

Id say for the riding you described an "all mountain" bike might be overkill. Id look at starting your search with a nice 5inch travel XC bike. As long as you dont huck it off 5 ft drops to flat a nice 5inch bike will be fine.

Heres my stab at it:
1. No.
2. FS will make those longer trips much more enjoyable.
3. Yes.
4. Depends, some will spend thousands to lighten their rides and others prefer a bit heavier bike for durability and will spend just as much to attain that goal.
5. This is totally rider dependant. I'm 240 and ride a Trance. My dream bike right now is a Pivot Firebird. The Trance is definately more XC suited though but doesnt slouch for AM either.
6. Weight, suspension action, travel, most importantly the correct geometry, and finally component selection.
7. The attributes that make carbon great on the road also hold true for Mtn bikes. Some question its durability off road but carbon has proven itself well.
8. Geometry, weight, suspension travel, parts durability.

"It used to be 12 years ago that FS was squishy when powering uphills. Is that still the case that on uphills you lose lots of power and what about on flats - does the FS just there bouncing in the middle with each pedal stroke?"
-- As others have stated suspension has come a long ways. My trance for instance uses the maestro suspension system that w/ a plain fox float r rear shock almost never bobs. Other designs such as vpp and dw link bikes are also very efficient.

howdy, heres my response:
I also came from road bike and still ride road bikes with my club on Sundays.

1. Body armor may be useful if you have rocky technical sections. but may get hot on long epic rides. After a couple of get offs resulting in fractures I have on order a shorty, with no sleeve and elbow/ knee pads. I have a full face helmet I haven't used yet. but will if I venture to technical down hills again.

2. FS will handle the rock gardens and ruts much better. The new rear suspension technology (DW Link, Horst, etc) just about eliminates and pedal bob. and the weight is minimal.

3. Hydraulic disc are the best way to go. 7" to 8" rotors will give you limitless braking power.

4. weigh it important but not critical, for you probably around 25 to 28 lb fs bike would be the ticket. I went froma 23 lb hard tail to a 32 lb 5" travel frame.the bike still climbs and pedals well. I only notice the weight when I am loading it into my car.

5. I ride similar technical single track, so I would recommend, Felt, Turner or Titus.
for larger manufacturers I like Giant, Gary Fisher and Trek. all in the enduro style or trail bike frame. 5 inches of travel, and slacker front end geometry. I use to ride a x/c bike by the low supensiona and twitchy steering were not desireable for single track.

6. All modern mt. bikes have evolved into very fine trail machines. maybe saddle choice. I recommed WTB Rocket V. ti

7. I've had a carbon fs and now have a alloy frame. With fs you won't notice any difference other than a little weigh gain. I recommend carbon if your going to race XC.

8. a XC bike is designed for racing on a closed course. usually groomed. Steering is fast and suspension travel is low. I didn't like the way the XC bike on descents. It felt like I was going to fall over the bars when dropping in. An all mountain bike will give you a more upright riding position a slacker steering for stable control on descents. the extra suspension travel is helpful even on the smaller stuff. You can just roll over the ruts and rock gardens.

go out and test ride a some bikes. you'll know after you ride them, then after you get one you will probably want another as you gain mt. bike riding skills.

I higly recommend a mt. bike skills course after you get your bike.