I just picked up a 2011 Rocky Mountain Slayer a month ago. After putting on a dropper post, it is the most fun bike I have ridden. The geometry gives it a feel of a DH bike when you drop the seat and attack the bars, yet seconds later, you can be in the saddle leaning over the bars boosting over a stone wall in a long climb.
I just did two days of New England riding back-to-back (5hrs fri afternoon, 4hrs sat morning) and Im not nearly as beat up as I usually would be.
As always, you'll be paying a premium if you try to get the perfect component package you want (I got the Slayer 30, so the Domain fork is rough, and the lower end Sram drivetrain is choppy), but bottom line, the frame is designed for maximum fun on the descents and being highly respected during the long climbs.
Dont just go by my review, checkout singletracks review and rocky mountains videos of the frame design
Jake, IMO, when you're looking for the "best bike" at a budget, you should first look at what's available in your area, since the pricing varies a lot brand-by-brand in different countries. If you post your choices here, then people can offer their opinion. One thing is for sure though, if you can find a bike you like on clearance (older model or whatever), you will get more for your money.
Also, you might check the AM and what-bike-to-buy forums on mtbr.com, and also use the reviews for feedback on bikes you are interested in, lots of good info posted there.
I agree with the second guy, it's good to see what you have in your area. However, AM is what I enjoy the most and I have ridden a Santa Cruz Heckler. I got a Fox Van 36 up front and Fox DHX 5.0 in rear. It's amazing. It climbs like a Billy Goat and descends better. You can look at videos I have posted and check strava for times. This bike works. Easy maintenance. Just keep drivetrain in good oiled condition and ride.
If I had to choose a different brand, I would probably get a Giant Reign. I rode the Pro DH course in Park City on one and it handles amazingly. An added bonus is Maestro Suspension has a great pedaling platform.
If I had extra money I would check out a Pivot Firebird, I haven't because I know I can't afford one so why temp myself.
I'd look for someone selling last years model or something of whatever you decide getting hundreds knocked off your price meaning your bike will hold it's value longer. my personal Fav bike that does everything you mentioned & more is a Scott Genius very light for hills & i still haven't hit anything big enough that it can't take. best bike i have ever owned.