I've been hearing contradicting reports constantly. I've heard not to bother with crunches/sit-ups until you're already pretty much at your weight goal, and then they're just meant to tone. I've also heard that crunches are a great work-out no matter what.

Does anyone have their own experiences with this form of exercise and results or the lack thereof?

Yes yes yes yes!!!! Worth it.

Not just crunches, but all core work. As you strengthen your core, it affects your posture as well as your overall strength and balance. I am much more able to do things that aren't necessarily "core" exercises, but require the strength and support of core muscles (freestanding squats, for example), as I've strengthened my core.

Also even if you can't *see* that 6-pack forming, you'll feel the results.

Don't get me started on "tone" though ... That's a rant I could get into for days.

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Crunches are great, as long as you do them the right way - make sure you are using correct posture when you do them or else it won't make a difference, plus you will strain your body. I put my hands behind my head when I do crunches, but ONLY for support, not to help lift me up by pulling my head up. I focus on using my abs as completely as possible to be responsible for doing the exercise.

Many people say crunches won't give you a 6-pack, even if you do 200 a day, and they are right. By itself, the exercise will not give you definition. But that is because there is a layer of fat over the abdominal wall, and unless you do enough cardio to burn it off, you won't see the results of your crunches. So just make sure you are doing both cardio and resistance/weight training to "tone" your abs.

Exactly what PhotoChick said. Having a stronger core helps you in other exercises, in everyday life, and once you lose the fat on top of them you'll be glad you built up those muscles.

If you're doing mostly crunches, I recommend doing some lower back exercises, too, to balance things out.

I think ab exercises mixed in with strength training and cardio are great. When I jog at the track, I do them after every mile.

I like doing core work but I despise crunches. I really, really, really abhor any long rep exercise.

For some reason or another my favorite core exercise are planks. I lean on my elbows on a low chair, and keep myself straight as a board. I've worked my way up to 60 seconds.

The great thing that I realized from working my core is that my balance is a lot better. So yeah, crunches, leg raises, and all that other stuff is still good for you even if you're not going for the 6 pack.

I second the planks. They are really tough, and they work the whole core. You can do them on your elbows, or on hands like the starting position of a push up.
While you're at it, do some pushups too

I don't know if crunches specifically are beneficial or not, but core/ab work definitely is great for not just toning by also balance and general strength.

Rather than just do straight crunches, I like to mix it up (following various strength training DVDs that I have) with straight crunches, inverse crunches, oblique crunches, bicycle crunches, etc etc. (there are a multitude) AND work in plank position (like push-up position, but hands are right under your shoulders). Exercises in plank position work all your ab muscles as well as your back, arms, legs, etc. In addition, I find that targeting back muscles also helps tone and strengthen the entire midsection.

I may have misunderstood, but crunches don't need to be something you do a million of. If regular crunches are too easy for you, you can make them harder -- for instance, by adding weight to the crunch or destabilizing them (doing them on a stability ball)... or then both... etc. Make the exercise so that after 12-15 reps you can really feel the burn. I've learned from my trainer that there are always more variations to try!