*takes the Base Set 1 Bills out of his Unlimited deck and throws them in the shredder* ¬_¬
Modified: 0/10
If it came before Mom's Kindness, it might get a 1. But not only is it a different named reprint, it's inferior to your other options. Use Buck's Training. Or Team Galactic Mars. Etc, etc, etc.
Unlimited: Can I give this a negative number/10?
Not is it useless for the same replacement reasons as in Modified, it even managed to go back and make a wonderful card for Unlimited useless thanks to the most-recent-text rules. Why PCL, why?
Limited: 6/10
Any draw power is good. But if you look at the other cards in HGSS that you'll get in Limited (and let's face it, this set seemed to have uncommon S/S/T cards show up a lot more often than they ought to have (relative to Pokémon cards), such as Copycat, Oak's Theory, etc, Bill still isn't that good - moreso since it's now a Supporter.
Bill makes me sad. If it were still a Trainer card, I would adore it. But since you can only play one per turn AND it stops you from using another, better Supporter (which is pretty much every Supporter EVER (Here Comes Team Rocket, you don't count!)), well...
Sorry Bill, ol' buddy ol' pal, you fail.