The scans are the best Clark could get ahold of. Most are pretty good, some are excellent. They should be converted to watermarked .pdfs sometime in the future, I have no idea where they would be in line.
As simple scans, these are not going to have the same level of functionality as the .pdfs created directly from the electronic files used for printing.
I happen to love the JG stuff so I can't give an unbiased opinion. Even with 3/3.5 edition this material is very useful, whether or not you'll feel the same is a different story. I'd suggest Tegel Manor and maybe Dark Tower and/or Treasure Vaults of Lindoran as good ones to try out.
Patrick