Nothing on the hyphen vs underscore issue has changed in the last year. I think some folks at Google were indeed upset that GoogleGuy let this tip go out public. It was almost immediately after this clarification he went into a LONG quiet mode!
I linked some test results, but they certainly were NOT mine! On the contrary, I wanted to show independent results. What I did use as "evidence" was my web design site (Yes, I know it looks like 1998, but...) currently ranks #1 for "web site designs" (without quotes) over 46 Million pages at Yahoo (+ Google in the past). I checked again today, and I'm still at #1 at Yahoo today (but over 45,800,000).
I can FLATLY state, if I'd been using underscores instead of hyphens, there is *NO* WAY I would've EVER got to #1 period. I researched it 4+ years ago and it STILL holds true! Take that with a grain of salt too if you want, but I'm being honest. My clients' sites are where the most benefit of this choice has been proven to me.
In my informed opinion, just like Google, Yahoo MUCH prefers the hyphen as well. I did try to pass this tip to GT last year, but noone seemed to take me seriously. Considering G & Y deliver 80+% of SE traffic, it's nothing to write off completely. FWIW, I've also reached #1 for exact same search at MSN (4 million pages) too.
Another BIG problem with underscores is you CAN'T tell from an underlined link if there is actually an underscore OR a space being used. Hyphens will avoid this!
If keyword1_keyword2 does not help EITHER keyword1 OR keyword2 being found individually, it actually hurts them BOTH at the same time! That is very serious.
If keyword1-keyword2 helps BOTH (at the same time!) why NOT always use that? That's ALWAYS been my rule of thumb and I am SO glad I've always stuck with it.
I'm glad to hear it is "relatively simple to change the url generation behaviour" in GTLinks now. Will it be too difficult to add in a new toggle for the next update? I sure hope not... I want ALL keywords in my directory to be found individually.
Adding the ability to do this will be a HUGE help for all of your new customers! If your existing customers wants to keep same format, there'll be no change at all as the default option could still be to use underscores as it's always been before. I'd much prefer you guys to build in a toggle instead of hacking default behavior.
I didn't start this thread to brag on my rankings. I want GLinks to be improved!
Sorry again to those who disagree, but I've done online design since dial-up BBS days at 300 baud and web design since the very beginning in 1994. I'm not some rookie. I normally don't share my "secrets" with potential competitors, but I'd like to help ALL of us in this community get an edge over all others who are using other software.
In this case, the fact that hyphens outperform underscores is no longer a secret.
Thanks to ALL who've joined in this discussion! I hope it has opened some eyes.
[ADDED:] Hey, I'm willing to be the Guniea Pig to prove it helps my own directory!