I've used the Hollow Earth wasters before. They're good. A tad bulky in the cross, but not that bad. Like Ed, I think their Ren Fair prices were higher than the website ones. I'd seen them at the Fair and was honestly quite shocked at how expensive they were... but now that I see they're normally the price of a Purpleheart, I understand better. After all, they have to pay for their spot at the Fair, so they have to bump those prices up. For anyone who knows better, though, you should clearly buy driectly from their website (or perhaps ask at the Fair if they'll price match to their own website).
I did try using a plastic one (loaner sword) at a class once. It was terrible when against a wooden sword; it of course had some "give" the wooden did not.
It will depend on the plastic sword, as some are terrible, and some are quite good. Keep in mind, though, that steel swords also generally have more give than wood along the flat.
Not the best scenario when the drill was about "foolin" (however you spell "feeling" in german),
In modern German, Fühlen.