So, as I understand the article:

1) they removed farm tractors from the proposed regulations (which was a big issue)

2) if you have a straight truck under 17,000 lbs, you are exempt.

3) if you run less than 100 miles (radius, I presume?) from your home operation, you are exempt

4) there are also exemptions during planting and harvest season, which runs from March 1 thru November 30.

Frankly, I think they have really softened the blow on this one. 

How many farmers in PA run more than 100 miles to farm?

And there was a reference to small guys going to hay auctions?  I just wonder how many small farmers going to hay auctions are hauling more than 17,000 lbs of hay?  I think the one place where it will catch small farmers is those guys running pickups pulling trailers.  That is the one place where I can see guys needing to get current.