The original 77's and the MK-II's are solid dependable rifles, but can have triggers that range from acceptable to awful out of the box. With a little tweaking most can be just fine.
The original tang safety versions were hit or miss as far as accuracy goes. The Mk-II's are generally plenty accurate enough for hunting. Most will shoot around 1 MOA with trigger work, but I've never shot a Ruger that could compete with other brands for pure accuracy. I'd still rate a Ruger at near the top of my list of guns I'd prefer to buy. Accuracy is good enough, and I value rugged dependability over a tiny bit of accuracy I may not be able to use anyway.
The newer Hawkeye's generally have much better triggers and have shot the best of any of the Rugers I've owned or shot.
The 280 is a good round, especially if you are a handloader. I wouldn't touch one if not. It isn't anything magical though. It won't do anything a 270 or 30-06 won't do just as well. It also doesn't give up anything to them either. I've had a couple of 280's over the years, including one of the Ruger's. If you just want something different from the crowd it is a good choice. If you want to be able to find ammo anywhere, not such a good choice.