Flat greens are boring. Flat green surrounds are also boring. There are some very enjoyable greens at Old Macdonald, for example, which tie into the surrounding bumps, hills, and hollows from the edges of the green inward. Many of the greens have slopes and tiers and small mounds whithin the green, but there are many pin locations that have a constant slope that allow makeable putts within 10 feet of the hole. Chipping or putting through several breaks is just part of the fun of getting to the hole. These are greens made with the spirit of the links.
Another example in contrast would be Bethpage Black. I can remember a lot of tv coverage from the Open talking about how subtle the contours are in these greens, etc. When I played there I don't remember the greens being particularly exciting. In fact they were pretty flat, with "subtle" or small breaks, I didn't find them hard to read, it just required that you actually look at the putt from both sides. I am a walker and I actually will read the putt on my walk up to the green, place my bag down, and then read the putt from the other side, or whenever possible. This speeds up play, unlike many cart riders who may or may not take the time to read the putt and instead stand behind their missed putt whining that the greens are too difficult to read.
The hardest greens I have seen and played on consistently are those at Cape Kidnappers, there is a general drain to the ocean that seems to slow down any putt away from the water. That being said many putts that appear downhill are deceptively slow, the opposite is also true on some holes. There also seems to be a myth about the grain of these greens affecting the speed of some putts, it then becomes very difficult to describe a putt to someone when they start to think about slope, ocean effect, and grain. I am not necessarily frustrated when I mis-judge a putt out there, I'm only looking to get a little bit closer to a tap-in. I don't know if the same can be said of the average golfer. When in doubt stop thinking!
The bottom line is that any green can be read with some effort and a little course knowledge (from your local caddy). Good greens should require a balance of touch and imagination and the ability to hit an agressive putt to the back of the cup.