NOTE: Wrote in November 2013 WOW, has so much changed. These were mobile.html built.
Mobile Design, often called responsive design is something new and so it does pull some hype. I think a lot of it is driven from people working with WordPress and since that is database, it is easy for a new person to work with it. However, it makes your creative design very limited. BUT, it does not mean that it is something new, cool and the direction future websites may go.
The question is if it is time to jump into one.
Every time I build a website, I try to create a vision statement and purpose the website is suppose to accomplish. Some websites like http://betsyshrift.com/ benefit with mobile response in the properties area because they can add QR codes to the for sale signs which are designed for mobile devices.
Other websites like a restaurant or storefront may benefit if people are looking for a number or address on their mobile device. Northwood Distillery puts a QR code on Heath Rum posters that take them to the mobile recipes page. But again these are QR driven and make more sense to have a website that is mobile friendly.
One solution is an automatic mobile redirect. It is more devices specific and still allows the user to go to the main site if they wish. Here is a couple that I did:
http://oldeworldpastriesplus.com/mobile.html
http://www.northwoodsdistillery.com/mobile.html
https://packerlandwebsites.com/mobile.html
http://www.abramsspotlightproductions.com/Mobile_Home.html (you can buy tickets via mobile also)
The bottom line comes down to, how many of your desired visitors are going to use a mobile device and why? I think I sell a lot of sites because I approach it as a marketing solution. I charge my client a one-time cost of $150 for this and since it is part of the main website, there is no additional hosting.
Responsive may be the best option for you and is something Packerland Websites offers. More importantly is determining what Internet marketing strategy will achieve the best return on investment and serve the purpose it is intended.