Okay, so I am a big fan of my iPad. I would almost feel comfortable getting rid of several of my cook books because of the app. I won't, because I want a back up, but that is how much I love these apps. I'll go over the top 2 apps that I enjoy, and you can decide from there.
Believe it or not, I have been using this site (and cook book) for a very long time. But, the iPad app simplifies the whole process. First, it has this AWESOME feature which allows you to gain inspiration, and it is literally called "Inspire Me." First, you select the course, then the ingredient, method and time. If you've paid for the Pro App, you also get the option of Occasion and Cuisine. Here's where the inspiration comes in. The app starts filtering pictures down, almost tetris like. Ones that you are interested in, you can tap the picture, and it brings up a summary screen. From here, you can decide whether or not you want to read the recipe, find more like it, or review it later.
The Allrecipes app also has a few nice if you purchase the pro version. First, a recipe box (bye bye hand written note cards). Also, a shopping list. I LOVE the shopping list, because I can quickly go through it, and check off things I already have, so that I don't buy it over and over, and have a concise, easy to access list of what I need from the store. If you're a last minute, short hour cook like me, who likes inspiration on the go, this is perfect.
The final part of the app, which is cool, is the way the app walks you through the steps. After you've decided what you want to cook, you tap the "Start Cooking" button. This brings the app into horizontal view, so you need to be sure you have a stand. It has a built in timer, for easy access, and you can quicklky tap through the different steps, which in a long recipe is really useful.
One downside I found for this app, is that it sometimes times out. and when that happens, the timer (for me at least) has quit working. Now, I just did a test, to see what would happen, and I tapped out of the app using the  button at the bottom of the screen. Then I reopened the app. The timer did go down. And I also used the top button to shut the screen off, and it still worked. So, maybe it was a one time fluke.
Overall, I give this app a big thumbs up as a necessary, late hour cook's app.
Next up: Epicurious
This app is nice. I don't have nearly as much to say about it as I do Allrecipes. One criticism I have, which I'm sure is up for debate, is the user interface (UI). The UI of epicurious seems to be slightly less friendly than AllRecipes. However, when I can't find something on AllRecipes, this is my back up app. It has similar functions, such as the shopping list etc, which unlike AllRecipes, is free, but in order to sync your recipe box (from your computer perhaps?) you have to pay $1.99 for it.
This short hour cook's preference is allrecipes, but this is an excellent contender, and one that I still use.
Ok, at this point, I bet you're slightly disappointed in my over zealous review of Allrecipes, and the lack luster review of epicurious. I guess, I'm biased. But these are two iPad apps that if you haven't checked out, you definitely should.