They also tend to have some pretty good loot in general, given the mix of enemies. Certain very large bosses at the end of them are like walking loot pinatas. Again, assuming you're high enough level to take them down.
I'm slowly grinding my final pre-Dragonborn character up to level 50 for the achievement. I've transitioned from pure archery to include daggers, and throats are getting cut left and right. I just went through a big fort filled with wizards and cut about 2/3 of their throats in the process. Incredibly satisfying stuff.
I've found I can combine my archer and alchemy to power level my one-handed, which is facilitating said throat cutting. I'll poison my bow with paralysis, which is good for 12 seconds per dose, two doses per bottle. Then tag some fairly powerful enemy such as a bandit marauder or chieftain, and while they're laying there helpless pull out the ol' dagger and wail away on them. If I don't finish before they start to get up, pull out the bow and tag them again, then back to the dagger to finish. Pushed one-handed up 10 levels in a couple days this way. (Playing on Master means everyone has plenty of health to work through.)
Level 44 overall now, about to hit level 45, which will make Luna my highest ranking character. She'll get to 50 on the basis of the three crafting skills (all in the 70-80's), pick pocketing, and one handed. I'll probably hit 50 right before Dragonborn comes out, at which point I'll re-roll a new character and dive in.
Over a year later, Skyrim still has me by the balls.
