I had one for years and decided to upgrade and got the All-Clad with white crock and stainless. Looks beautiful and cooks fine. Got it at Wms-Sonoma because Bed Bath & Beyond only sold it with black crock. W-Sonoma is great about returns if you want to try it out to see if you like it.
I am in no way an expert, but here are some things for you to consider when it comes to crockpots.
A removable crock is helpful for washing up, etc.
A crockpot that switches to "warm" at the end of the cooking time is nice to have, if you're the kind of person who, like me, starts your crockpot in the morning when you leave for work. If your 8 hour days suddenly turns unexpectedly into a 10 hour day, you know your crockpot will just switch itself to "warm" when it's done cooking rather than keep on cooking and burn everything...
There are a couple of different sizes--I think I have a big Rival oval 5 quart one that I've had since about May and I like it a lot. It's almost always big enough for everything I need to do. I have an older (from the 80's, also a Rival), smaller, round (2 1/2 quart I think) one that I use as my back-up. I also have a little bitty one (a Rival "Little Dipper") that was a gift that I occasionally use to keep dips warm at parties, etc.
I've seen (rival) crockpots that have a mechanism that "clasps" the lid on tightly. If you're thinking you'll be dragging it to potlucks and picnics and such, it seems like a nice feature. I think the same crockpot also has a spoonrest built into the lid, which I think would really come in handy.
If yours comes with an insulated carrying case, it's nice to have.
Based on a recommendation I got from someone here on chowhound (can't remember who at the moment), I bought a "special edition" Rival crockpot that comes with a removable crock. It's called a "VersaWare" I think. The crock is unique because it can also be used on the stovetop (or in the oven) if you want to brown things stovetop (or finish in the oven) in the same crock you're slow cooking in.
To be honest, I haven't used that feature of that crockpot yet (I got it in late May and it's not been "crockpot" season since I've had it, but, rather, grilling season) . However, that same crockpot has two other unique features that I LOVE. First: You can set the cooking time in half hour increments. So, for 4 hours or 4 1/2 hours or 5 hours or 5 1/2 hours or 6 hours or 6 1/2 hours and so on. My previous Rival crockpot only had five settings: 4 OR 6 hours on "high"; 8 OR 10 hours on low; OR warm. The flexibilty to set the time however you want at either high or low is pretty great. (And it has "warm" too).
Second: it has a countdown timer so you know at a glance how much cooking time you have left. Otherwise, you have to do the math, "Let's see, I set the timer for 6 hours at 10:15, and it's 2:00 now, which means the amount of time remaining is..." Not that it's that hard to do, but, if you're a bit forgetful like me or you have other people in your household interested in the cooking process, it's a nice feature.
I bought a Rival oval 6 quart about 3 years ago and it died on me earlier this spring. Also, the handle on the lid broke off. Until then, I was pretty happy with it. I wouldn't say I was a heavy user--I used it maybe 1 or 2 times a week from Nov-April. But, I guess they aren't made to last anymore...
Also, a lot of people say "new" crockpots run hotter than old crockpots, so, be careful in using "old" recipes... I don't personally have enough experience to say whether this is true or not.
re: The Dairy Queen
My newer Rival cooks much hotter than the one from the 80's. It can become an issue when I figure time as I did for the old one. Some stuff will become mush.
I love my newer one, it lifts out to wash. As to locking the lid to take someplace, I use large rubber bands.
I think if you have room and the money, buy a large and a small one. They are great for soups, roasts, to keep warm appetizers at parties. And if you can find it buy the Bar B Q crockpot by Rival. It is the only way to cook brisket.
Slow cookers and crockpots are, essentially, the same. At least, when most people talk about them, they use the names interchangeably. I find they're awesome, but I also use mine quite a bit.
I have 2 cookbooks for crockpots: Not Your Mother's Slow Cooker and Fix It and Forget It (this one actually has a few variations of cookbooks).
Honestly, I don't use either of them much, although I have friends who do every time they use their crockpot. Generally, I use the crockpot for stews, dried beans, chicken stock, and most braising recipes. Any recipe I have that involves getting a tough cut of meat tender, I'll use the crockpot. Pulled pork comes out nicely, too.
Crock-Pot is a trade name that is sometimes used generically to describe slow cookers in general. Like Xerox or Coke. Don't know that they're rave-worthy, but they certainly are useful kitchen tools. No ideas about specific cookbooks, but any braising recipe will work well in a slow cooker. And I've been playing with mine to do sous vide, but that's a whole 'nother thread.