In terms of the latter, the prep is as easy as can be. The night before, you pour 8oz of some kind of milk (I use 1%) into the blender bottle (you do not really have to use theirs if you have a lot of them, there is nothing special about it) then pour the contents of the packet on top of the milk, shake it up and put it in the refrigerator to sit overnight. All that takes a grand total of about 45 seconds. In the morning you just drink it as you would any protein shake. No blender is needed, and the cleanup amounts to washing the bottle out after you drink it, which takes another minute.
I tried all three flavors in the starter pack and liked them all. I liked the apple cinnamon flavor the best and the strawberries and cream flavor the least, but I was not choking them down like I have done when drinking some meal replacements and protein powders in the past. The consistency is a bit funky (at least for some). It is like drinking cold, runny, instant oatmeal. Although it tastes much better than cold, runny, instant oatmeal would. You can make them runnier or thicker by adding more or less milk, but I find just using the 8oz is fine for me.
The one drawback for some is that they are a bit pricey. I get the subscription through the Oats Overnight website, so the price per packet is a bit lower (about $3.50). That is much cheaper than getting coffee and a donut, or a breakfast meal at a fast food place (and much healthier), and comparable to or less expensive than many meal replacement shakes (especially the RTDs or the packets). And for me, since my lunches and dinners range from about $7-$9 per meal, it is less than that. So how cost-effective they will be for you will really depend on what you currently do. If you usually make breakfast, these will very likely be more expensive than what you are making. If you are on the go and grab something to eat every day, then this may present you a healthier option at a comparable cost.
All in all, if you are looking for a healthy breakfast option, that is easy to make and gives you a great mix of nutrients, and these are friendly to your budget, and you think you can handle the texture, I definitely recommend them. I cannot say that every flavor they have available is great tasting, but I have no complaints about the ones I tried.