This is a good and reliable way of doing it... Depending how server savvy are you are, you could alternatively password apache. (If that's what you are using- it's what we currently do to keep the bots out)
Previously you could get around it by adding an index.html and a <no follow> to robots.txt
You would make the html page the default page and work on index.php
Now the reason I am mentioning this is if in case anyone comes across the post I made. A while ago that method worked, however with SEO on the forefront of most web dev's mind (aesthetics to one side) sites and forums are made for SEO.
Xenforo is clearly well written for SEO as even with my no allow - index.html, I've not submitted any links - the site has been crawled and displayed perfectly in Google - although I didn't want that, it shows that XF is excellent for SEO..
Don't use the index trick, it no longer works. Htaccess is the only way to do it...
Sorry but I had to correct myself and explain why just incase anyone does do it.