I agree that this is a very underappreciated series. The coins are beautiful and interesting. The prices are still very reasonable, at least compared to other U.S. coins. However, it can be hard to find a good dealer. And, there are MANY counterfeits. Finally, lots of the available US/Philippine silver coins have been improperly cleaned. So, if you find a nice example coin, but it before it is gone. Most of the coins you can find are from 1944/1945, brought home by American soldiers, and are pretty common. The coins from the 1920's are challenging.
I also have taken an interest in the coins made for the Culion leper colony. If there is any interest, I can write up an article about them.