Oh, I love sharing this experience.
Do you know the Intel Core2 Duo E8400? If not, then I'll just say that when it was new, it was regarded as just about the best gaming CPU on the market. I had mine at 4.0 GHz and I loved it! Its stock is 3.0 GHz, it has 6 MB of cache, and it's a 45nm CPU (err, it uses the 45nm manufacturing technology). I upgraded to this CPU from an Intel Pentium E2180 which is a dual-core CPU with just 1 MB of cache, and it has the 65nm manufacturing technology. When I upgraded to the E8400, I thought it was a huge upgrade because I felt quite a noticeable difference.
However, that was nothing. Last year, I upgraded straight from the E8400 to the 2500K. This upgrade makes the upgrade I just described look like a baby step. Omg. There's a reason why I named my rig "It's like advanced alien technology". This thing is fast and it's powerful. I noticed a difference for everything I do.
There's one difference that I'll explain that I have fun explaining because it's just a piddly little thing, but for me it was pretty big. I have the Control Panel displayed as a menu on my Start Menu. When I had both the E2180 and the E8400, the Control Panel would take about 2-3 seconds to appear on a fresh boot. Of course, once it loaded from memory it would open instantly. With the 2500K, the Control Panel now opens instantly on a fresh boot! I literally mean that it opens just as fast as it does when it's loading from memory! The first time it happened, I had to do a double-take. Then, I rebooted because I thought maybe I had already opened the Control Panel but simply forgot that I did. Nope. Right after the fresh boot, I made sure that the first thing I did was open the Control Panel. Bam! It opened instantly. My jaw hit the floor after that.
From that point forward, I would open the Control Panel several times a day just laughing at how fast it opens now. :) Although, everything is faster now. My entire computer just looks at me with its eyes half shut going, "Are you ever going to challenge me? Sigh" hehehe I ask it to do something difficult, and it just does it like it's the easiest thing in the world. Then it goes, "Yawn. Next."
I've never had an AMD CPU, but I heard that their current offerings are slow in comparison to Intel's current offerings. This includes all of the competition for Sandy Bridge. I don't know what Intel's doing to these CPUs, but they are very well-made and very efficient. I recommend trying one!