How you measure your progress is entirely dependent on what your goals are. If your aim is to improve endurance, increased repetitions and/or decreased rest times are good indicators; if it's changing your body composition (less fat, more muscle etc.), then weighing and measuring yourself is the way to go; if it's pure strength, then increasing the weight once you reach a certain repetition range for each exercise will allow you to progress and continue to make gains.
It's easy to get caught up in the idea of progress for the sake of progress and even easier to become disillusioned if you don't feel as though you're making any. It's possible to make progress towards improving your strength while using the same weight of kettlebell even though it may feel as though you're stuck because you're still using a 24kg bell for swings or some such. I find that, especially where numbers are concerned (weights, reps etc.), it's very easy to lose sight of your original goals and feel like you're not getting anywhere if you're focusing on the wrong things.
I hope that makes sense.