Yes quite a bit, but it always depends on the quality and steel composition of the saw blade. I am glad that you have had success with using them, I'm a big proponent of re-cycling. I in no way want/intend to dampen your spirit and desire to use the material for making knives. I'm some what addicted to the craft myself. Lot of old sawmill blades hanging round down in your neck of the woods (if someone has painted them up). Are you forging and re-heattreating or cutting out and grinding stock removal style?
Thing to keep in mind, they are not all equal for a large variety of reasons. Extensive testing to get the correct thermal cycling for the best performance from any "mystery" steel is highly recommended.
We sometimes get lucky without testing, but there are so many variables in the steels used for saw blades - some for good reasons, some for economy, some because of availability, etc. My experience has been all across the spectrum of suitability from excellent to highly disappointing, so I test and I thermal cycle all the steel I use for making blades.
Brand names used to mean a lot but not so much anymore as majority are imported and usually mediocre to poor quality steels or are composition/bi-metal construction. It's a can of worms for most makers and they prefer not to waste time to figure out what's what with sawblades.
Mostly....if you are having fun, it's all good.
ps - next Georgia Custom Knifemakers' Guild meeting will be across the state from you over in Statesboro at the shop of Twin Blades. This will be in Feb (date not set). You are welcome to attend.