Don't be fooled into thinking that this is a food show. Sure, there is some cooking going on and you may get the odd tip about bread baking or something but that's not what the show is really about.
It's basically a more grown up version of Big Brother, for older, normal people who really should no better. The best bits of Big Brother are where they are made to compete against each other or when they are given loads of booze and get drunk. That is what happens on come dine with me in every show, at the same time. To finish it off you get to see people rummaging through each other's houses, occasionally finding something amusing.
As such, the show is incredibly dependent on the quality of the contestants however, so it can be a little hit and miss, but there is usually something worth watching every week.
It's a great show to watch with your girlfriend/wife/partner, but be warned, you'll probably end up arguing over who's the most annoying or who is cheating the most. One of the other problems with the show is that it's really not that hard to cheat. Just mark your competition with 4s and 5s out of 10, maybe even lower if you can and you're bound to win. Oddly, it seems to be mostly women who lower themselves to this tactic and the group occasionally sense what they are up to, which can be fun.
The show is at it's best when the odd couple groupings pay off and the group all get along when you least expect it, or theirs only 1 grumpy miserable contestant who alienated them self from the group. Even better, when there is one particulalrly cocky contestant who boasts about how great their cookery is. only to make a complete mess of their evening.
There are people who you sympathise with, people you you will hate, people who are like that annoying person in your office that you have been trying to explain to your significant other just why they annoy you so much and you will point this out them and they still won';t understand what your problem is.
In short, it's a great show, and I love it. The 30 min shows are the best. The hour long shows don't show enough of what's going on or let you see them going through each other's houses, but that format works well for the celebrity versions as you know who they are and it's enough just to see the dining part.