If you can't spring for the ridiculously priced DA or SRAM Red cassettes, Ultegra offers great quality, reasonable weight and a wide variety of gear-size options for a very affordable price point. I own at least six of these cassettes, in various tooth sizes, and they just do what they need to. Before living in Maui, I raced CX every year in Oregon and used these cassettes in brutal conditions where they'd get completely abused, packed with mud and debris and forced to keep on going. After post-race clean up, they were good as new. Important to always grease the splines on the cassette body when installing to extend the lifespan of both cassette and cassette body.
When the road bike had about 16,000 miles on it, the shifting started becoming erratic. The chain would jump between gears on the rear cassette, and cleaning and carefully adjusting the rear deraileur didn't help. I replaced the cassette, the chain (which only had about 4000 miles on it), and the shifter cable, all at the same time. Now the shifting works fine, but I'll never know if it was the cassette, the chain, or the cable that fixed the problem. The cassette is well made and easy to install if you have the right cassette tool and chain whip, otherwise it would be very challenging. The next time I encounter shifting problems, I'll start by just replacing the cable before replacing the more expensive parts.
I find Ultegra cassettes bullet proof and a good value for my training bike. They are relatively inexpensive and last a long time if you take care of them. Highly recommended.
Finally gearing that is intermediate between Mountain and race. The 12-30 10 speed is perfect on my cross bike for some serious off road and touring rides. Shimano quality is also a big plus - quick shifting and durability is a given. I bought the cassette for a loaded tour and now use it to take on local MTB trails. It has made the cross bike more versatile and fun. I would recommended for adventure rides, steep road climbs and tours!
I am still running 10 speed. Needed a new cassette for a new Hed wheel. For $XX, these are incredible deal! The finish holds up really well, too. Seems to be more durable than Dura Ace for a lot less $ and just a little more weight.