It gets some good reviews - but if you can hold back 25% ink without losing quality, we should be hammering on the doors of the printer makers.
I think the answer is that Inksaver CAN work, but just how much saving it makes depends on if you want a small saving with still good quality, or to get down to deeper savings? - If you can get away with refilling, the break even point will be pushed a lot further back.
JR often feature on QVC - Friday Midnight is usually technology (if it's not Gem week or something!) and if it's the TSV, you get plenty of demonstration.
Serif had something bundled with Inksaver on a flyer a while back, but I think it was only V1 - I also saw V1 on a £6.00 computer fair CD - full version, fully legit (they don't warez at my local fair, just like we don't warez here)