What components are recommended for entry level mountain bike? I am looking for an entry level mountain bike. I plan on using it on real mountain bike trails, not just unpaved trails and greenways.

Specifically, here's what I'd like:


good shifters/derailleurs that generally change gears in a predictable fashion
good front suspension
rear suspension would be nice if I can get it without entering the "prohibitively expensive" zone, which for me is basically the four-digit range (maybe $1500 if it's too good to pass up)
not opposed to a used bike
it's ok if the bike isn't super light or made of the same stuff as the space shuttle


And are there some important considerations that I'm totally missing? The purpose of the bike would be to noodle around some of the excellent trails in Utah County, so the bike would take a bit of a beating from time to time.
Here's the short list of should haves in mostly descending order:


Coil or air sprung fork with rebound adjustment, minimum of 80mm travel. Specs any lower than this aren't actually meant for actual mountain biking. Maybe a little unpaved riding, but not mountain biking. Replacing a fork is expensive. Buy a bike with a fork as described and the subsequent parts listed here will almost certainly follow.
Double walled rims. Single walled rims suck and you will trash them. Double-walled rims are almost always stronger and longer lasting, and often lighter.
At least an 8 speed drivetrain. I'm just talking about the cassette (the rear gears). Multiply that with the 3 up front and you've got 24. This will give you decently tight gear ratios and keep you clear of the low quality parts that come in 7 speed configurations. If you're willing to spring for it, go 9 speed as much for the quality increase as anything else.
Mechanical disc brakes. You can get by with V-brakes, but a nice pair of mechanicals (typically Avid BB5's or BB7's) will make a world of difference in terms of modulation. A word of warning though, some entry level hydraulics are worse than decent mechanicals. Make sure you try them and make sure they stop you before you buy. All disc brakes require a good handful of hard stops to achieve maximum power, so keep that in mind as well when test riding.
Freehub rear wheel. Stronger and more durable than the older style thread on freewheel type hub.
Cranks with removable chainrings. Cheaper cranks have riveted on chainrings which means when the chainrings are worn out you have to toss the whole crank. That's lame.



Here's what not to get if you're looking for best bang for your buck in a beginner/intermediate package:


Anything full suspension. Just don't bother at the low price point unless you have a really good reason. You'll get way more bike if you stick with a hardtail.
Anything other than an aluminum or maybe steel frame. Aluminum is going to be the most common, steel usually disappears at the intermediate-ish price points, and then re-appears at high end price points. Aluminum is likely your ticket.
Anything from a department store or anything from a brand that also sells at department stores. The brands that have fallen from grace have been bought up by big conglomerates and prey upon people with brand name recognition, especially at lower price points. Avoid.