It's definitely better than the first one, but pretty much only because it takes longer to become completely boring.
You use the stylus to chop, peel, dice, mix, knead, grill, stir-fry... just about any cooking command you can think of. The original Cooking Mama used the stylus quite primitively. However, in Dinner With Friends, you'll find that pressure and speed are a lot more important. You have to find the balance between finishing the step on time, and not spoiling the ingredients or sending them flying. However, it's really not that challenging to find this balance, which is why I was a little disappointed in the long-run.
With the first Cooking Mama, once you unlocked and cooked all the recipes, you had yourself thinking, "Well, now what?"
In Cooking Mama 2, they basically just added a load of more recipes to make the game last longer. However, they did add a few new game modes. Unfortunately, they're not so different from the first one. You have an option to cook with different friends, which is essentially taking the entire repertoire of recipes, dividing them amongst 9 or 10 people, and having no instructions screens before each step. They also made it a little more tricky by not giving you much room for error- else you'd be forced to retry.
The game also gives you a lot of unlockables. There are accessories for Mama, including outfits, and you can change the colours of the kitchen and the various utensils.
The rest of the unlockables are seals for your cooking diary, where you can put in pictures of the food you cooked. Lame.
Over all, this game is decent. But it's only decent while you're still unlocking recipes and such. After that, you won't find much reason to play it anymore. I wouldn't recommend spending money on it, as that could be put to much better use in these dire economic times.