Don't hold your breath for a response Chris, although I may mistaken...there are no secrets out there, but THEY think there's are.
According to Bobby Palkovic at Merlin, he feels that the lead free version of his loudspeakers are clearly superior to the products he has previously built, and that the current product are easily his best ever.
I've been around his speakers for a while, and do feel the sonic qualities of the product are of an exceptionally high level.
As for me, I am the importer in the USA and Canada for Opera Audio/Consonance, a manufacturer who does most of their business in Europe, and have been RoHS compliant for a few years now.
The sonics of our gear speaks for itself, and I hope over the long term, through audio shows, get togethers, and through the dealer network we build that I will be able to prove just that to everyone.
But, at least as important, the six or so months I have served in this role has made me feel confident enough in the build quality/reliability of the product to the level that I have just instituted a fully transferable 5 year warranty on most of our components. I want to instill that same confidence in the hearts of our customers, as well as the peace of mind a long term care/relationship provides.
The legislation applies to all the electronic parts, not just the solder.
The 4 main negative issues with the lead-free solder are:
1. Precisly controlled (and higher) temperatures must be maintained for good joints.
2. It's brittle and joints can develop cracks.
3. Prone to growing "whiskers".
4. Makes equipment is more difficult to repair.
The EU is still allowing lead solder in critical applications such as aircraft and weapons electronics, because of reliability problems with the lead-free stuff so far.