We bought these trays a few weeks ago, shortly before the birth of our second child. For our oldest daughter, we always used the bags, which worked out fine, but we found ourselves wasting quite a bit of milk with those, plus they were quite expensive to purchase. Our youngest daughter is now a month old, and due to an oversupply issue, I had to pump pretty much right away. So, while I haven't used these for an incredible amount of time, I can definitely say these are well worth buying.PROS:- Cheaper than milk storage bags. To me, this is a huge pro considering with my over supply I could easily go through 3-4 bags a day while still nursing exclusively. We just freeze them, pop out the "milk sticks," then put them in a Ziploc and label the baggie, then throw it back in the freezer. Yes, the sticks to stick together a bit, but they come apart easily and don't break.- You can thaw just the right amount of milk. You can take a bag full of 8 milk sticks and only grab 4 and keep the rest frozen if needed. This cuts down on wasting milk.- You really only need to buy one set of trays unless you have quite an oversupply. That will allow you to freeze 16 oz at a time, which probably won't be needed for most women. At the most, I do 8 oz right now, so I have an entire tray left still. I think I will be purchasing an extra set for the purpose of donating since I have an oversupply.CONS:- It's a little difficult to tell where the 1 oz mark is, but I usually just estimated and tried to make them even.- They probably take up a little more room in the freezer than freezing the milk storage bags flat.- You can't fit more than a couple milk sticks in the smaller 4 oz bottles. We were only able to get about 3 in those bottles, so we often would use a separate cup or bottle (the larger 8 oz ones) to thaw 4 oz of milk. Not sure how to get around this just yet, but they are small enough to fit in the opening of pretty much any bottle.Yet, those little things don't make me rate these any lower than 5 stars. I highly recommend these for breastfeeding mothers, especially if you want to be economical.