My honest opinion? Considering I am a non driver in RL I had a great deal of fun! Zipping around the tracks trying out the huge loop-the-loop on Nissan island, finding the code to get your own free car or answering the challenge of Mazda, jump the gap and keep the car :) (It took James 3 tries LOL)
From what we saw Nissan have certainly got the right idea of how to show their product to its best advantage with plenty of information and a lot of fun activities which had kept people coming to the sim even though there were no staff on hand at any time we visited, there were still avatars having fun. The only disappointment was the boxy look of the virtual model, with sculpties nowadays a better model could be constructed although the internal detail was good. Mazda also was populated and set in beautiful surroundings too. The Mazda Hakaze was also one of the best built representations we saw, although, only having a simple drive script it may have limited real drivers enjoyment.
How should Real businesses set about using Second Life? Well I am no marketing expert but if you don't make it fun and give people something to do then you are unlikely to succeed. You need to provide the information in a fun and interesting way, I believe Nissan have seen the possibilities the best out of the ones we visited, closely followed by Mazda.
To an extent it's the same as browsing the Internet for information on cars, BUT its much more fun and relaxed, Why go to a stuffy showroom if you can walk on a tropical beach and and enjoy the looks of your new car at sunset?
Can Second Life be used to sell real products? I believe it can if it is done in the right way. Just don't take us all for suckers and give us some real info to go with the free models!
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Addition : Second Life was much more in the public eye than it is now, seen as the darling of the tech media, and attracting attention among those whom would ordinarily dismiss such things as "geeky." It was to the point real life businesses wondered if they could use Second Life as a means to make money. I myself saw numerous companies such as Circuit City, Manpower, IBM, and many others here. Among these were car companies.
Real life companies more often than not found Second Life a confusing
place. It didn't help that most didn't try to recruit local talent, but
try and learn and do things on their own. As James and Dana wrote, the
results were often disappointing for Second Life residents and real life
companies themselves as they didn't get the results they desired.
Eventually, the car companies would move on, leaving the Second Life
auto market to local talent.