How much of a speed increase will I see with the base 21.5" model?

[Solid.Snake]

OK so my current (and only) PC right now has the following specs:

-512MB DDR2 RAM @ 200mHz (minus 64MB because it is shared with the Video memory)
-Intel Celeron 3.06gHz
-64MB ATI Radeon XPRESS 200 Series

It scored a measly 1150 in the Geekbench benchmark test.

So if I buy the iMac 21.5" (4GB RAM, 500GB HDD, Core i3) how much of an increase will there be? How many programs can I have running while they all maintain a really good speed (something along the lines of iTunes, IM software, a video game, internet browser, etc.). I might get the Sims 3 for it, but not much else (got a PS3 for FPS and such).

And for those people who switched from a really old PC (such as mine) to an iMac, or any other Mac, what was your first reaction (other than the beautiful looks :p)? Is it still going strong (in terms of speed) or do you notice any speed decreases anywhere?

[Hellhammer]

iMac can handle dozens of apps at the same time without slowdowns. I switched from an Acer laptop to an iMac and haven't regretted. No slowdowns even if I was doing something heavier with HandBrake for example. The new iMac is even faster than mine so it will be good for you for years

[Solid.Snake]

iMac can handle dozens of apps at the same time without slowdowns. I switched from an Acer laptop to an iMac and haven't regretted. No slowdowns even if I was doing something heavier with HandBrake for example. The new iMac is even faster than mine so it will be good for you for years

So how is your iMac in terms of having HandBrake running and doing some other stuff (email, Internet browsing, music, etc.)?

[Hellhammer]

So how is your iMac in terms of having HandBrake running and doing some other stuff (email, Internet browsing, music, etc.)?

I don't notice any difference even though HandBrake is using ~95% of my CPU. Everything works as it should