We opted to go to flash for several reasons.
1. 99% of the people that hit the site have high speed internet.
2. Most studio's around here have really crappy html sites, and we have had several people email us and book based on our site looking far more professional then the rest, quality of photos being equal.
3. Flash seems to be creeping up to be the new standard. A lot of the best photographers in the world now use flash, or have a large portion of flash on their sites.
4. 99% of our clients are 35 and under, and are into the digital age. Meaning they like the fancy gizmo's and gadgets. They all want the latest and greatest things.
5. We use a bludomain template, which is so easy to update, upload, change, etc... a monkey could do it.
As far as music goes, I think its just personal taste. We have music, 5 songs to listen to. I see more and more flash photography sites popping up everyday with music. My thought process is this....If a potential client is to lazy to click the stop or pause button, or they are going to piss and moan about something as silly as a song, I don't want to work with them. I also don't feel I should have to hold everyone's hand and post billboards on my site explaining in great detail how to click on a gallery.
That is just my opinion though, and I do still see some very well designed html sites from time to time.
And in us going to a flash site, and potentially losing clients.....since the site went live, my visits have tripled ( went from 30 a week to 100 a week), search engines hits have doubled, and we went from getting a couple inquiries a week to couple a day. In the last 2 weeks I have booked 2 weddings, 1 family shoot, 2 baby shoots, and 2 seniors.
So, flash seems to be working for me, could just be a fluke though..... Every area is different though. What works for some won't work for others.