I personally haven't heard of anyone bricking their Kindle by installing the screensaver hack. I suppose there is a risk, but I really don't think that it's any bigger than installing a official update. I mean how many people haven't tried it as of yet with no problems? And besides Kindles ain't like people and medicine. They're born pretty much the same.
There could arise other problems by installing a hack than a total breakdown, eg. losing the warranty. But it seems Amazon don't mind with the screensaver hack anyway.
I'll say go for it.
You sometimes just have to dance with the devil, right?
Cheers !