Recently I have found that Artisteer 4.0 has an option for creating mobile device layouts. It means the template created by Artisteer 4.0 supports both PC and mobile device.

I am wondering if mobile Joomla extention is really needed to be installed in case the template is created by Artisteer 4.0.
I would appreciate any advice or comment on this subject
Thanks.

I don't know for sure how Artisteer creates the mobile layouts, but my understanding is that they just scale the layout of your web pages for mobile, meaning that they do nothing to actually optimize the page size for faster mobile downloading. So if your web page is 2MB on desktop, it still is 2MB on mobile even if the layout looks nice, but downloading the page will take an unnecessary long time. If that is the case, you would be wise to also use Mobile Joomla! to streamline the page sizes and speed up download times on mobile.

If you have your page up and running already, you could also try our Responsive Template Analyzer to estimate how much faster your site could run with Mobile Joomla: http://www.mobilejoomla.com/responsive-template-analyzer

Thank you for your good advice. It is very helpful for me.
One question comes up. Mobile joomla provides templates for mobile device.
If both responsive template and mobile joomla are installed, which template is used or effective for mobile device?
Is there any confliction with those templates?

You can freely select which template you want to use for each device profile in the MJ settings, see here. So there won't be any conflicts.

Thank you for quick answer.
One more question. According to the announcement,Joomla 3 is mobile ready.
What is the relationship between mobile Joomla and Joomla 3?
What is the position of Mobile Joomla in Joomla 3?

Hi,

Mobile Joomla! is ready for Joomla 3.0 already. The position is pretty much the same as in regard to any other responsive templates: please read more from our blog post.

In short: we believe that server-side mobile optimization (like Mobile Joomla) is still necessary for most websites to truly optimize the page sizes and loading times for mobile.

We expect that one of the major benefits of Joomla 3 will be standardizing the UI functionality of most extensions (hopefully the developers will comply), which will make them much more easier to mobilize (instead of the custom solutions we have needed to do for Kunena and JComments so far).

-Miikka

I believe I have a similar question. I downloaded the  mobile Joomla extension even though my template is already optimized for mobile usage. I did not like the way my template was viewing on a mobile device and was hoping to fix it with mobile Joomla. Is there any way to use mobile Joomla to just re-scale my current template? I was able to re-scale images but not whole modules. 

No, MJ doesn't rescale template. But in most cases it's sufficient to

1) add viewport meta tag to the template
2) add "img{max-width:100%;height:auto}" to stylesheet file
3) don't use large hardcoded size in page sources (like <table width="1000">)

Other issues (if exist) usually may be fixed using media queries in stylesheet file.