What is your view using mac pro 8 core 8 GB system for software development? I have never used Mac system before but I am considering switching to Mac Pro 8 core 8 GB model. Currently I am using Linux box based on Dell Core 2 Duo with 4GB ram (that is maximum it can have). I am running into performance issues and sluggish application startup especially Natilus file maanger. Usually I have multiple applications running at same time.

I also need to run windows virtual machines for software testing.

If I invest in Mac Pro system:
Would I get much better performance?
Would I be able to run Windows as virtual machine within Mac Osx?
Would the learning curve be easier in terms of radically different UI on Mac Osx?

What about SSD disk on mac pro? Does it make very visible difference in performance when running applications?

One huge benefit I will get is to be able test web applications under mac osx/safari and as well as be able to develop for iphone and ipad.
You will definitely get a performance boost by upgrading from the Linux box to the Mac Pro. However, I don't believe that you'll see a huge difference in terms of actual performance between that Mac Pro and, say, an iMac with a 3.6Ghz i5 and 6 or 8 GB RAM.
As long as you're not doing a lot of gaming or other graphics-intensive or math-intensive things, the iMac should seem to the user almost as fast as the Mac Pro.
There's no harm getting the Pro, but I think you may as well save yourself the money...

As for running a VM, that's easy. You can even, with Parallels Desktop or VMware Fusion, run Windows apps and Mac apps side-by side.
Other software to look into is Boot Camp (free, supplied by Apple, restart required to switch systems) and Sun/Oracle VirtualBox (free, no restart required, some features missing).

As for the learning curve: It's not too bad. Lots of people make the transition. IIRC, 50% of Mac purchases are first-time Mac users. Apple offers a Switching 101 guide to help you out. Also, if you're used to Linux, you'll catch on quickly. Besides, most of the CL stuff is the same, so you'll always be at home there.

As for SSDs: They're really, really fast. You can see various tests and comparisons run by manufacturer OWC here. For best shock value, watch their video where they race an SSD machine with an HDD one to boot and open apps from CS5. It's pretty amazing...

A cordial welcome to the world of Mac!