I love egg white powder. Been using it for years in overnight oats and as a supplement to my omelets. Also put it in the occasional smoothie/acai bowl and mix it in with Greek yogurt. Aside from the Greek yogurt, I can't taste it at all. It has a really fine consistency, so it mixes in well with a lot of things. Just don't add it to hot liquid or you'll get egg drop soup.
To mask the flavor when I add it to Greek yogurt, I add smashed berries and a little PB vanilla almond powder and honey or stevia.
The big disadvantage is the price swings a lot. It started out really cheap, but sometimes it almost doubles in price. I can usually find it on some sort of sale, and the price does come back down (only to go up again). It's similar to the fluctuations we see with eggs, but worse (and the price changes lag behind that of eggs).
My favorite is the NOW Foods brand unflavored in a 5 lb tub. They also make a vanilla flavor that is good in smoothies. I've never tried the chocolate. This brand also tends to be the cheapest. The 5 lb tub has been sold out for a while, so I've been having to buy the 1.2 lb tubs. NOW adds BCAAs to their egg white powder.
IHerb and AllStar Health typically have the best price along with discount codes. Amazon sometimes has a matching price, but often it's sold out or very expensive.
If you can get 1.2 lbs for $30-$35 or 5 lbs for under $80, it's a good deal (when I first started buying it, I could get 5 lbs for $50-$60).