Oh, so you don't like Web 2.0 Gradients? I see, just flat grads. I get you. I like them, where as you see 'bulky' tubes I see a tube with depth and shine compared to one that is flat and boring. Web 2.0 is all about flashy gradients. :P
I think you'll agree that Web 2.0, is way past its time. It was introduced 5 years ago and everyone started doing glossy, colourful and oversized typography. I personally believe that nowadays we're moving more towards slick, undistracting, magazine-like designs. The gradients you see at http://dribbble.com are pretty subtle and slick for user interfaces.
Flat can still have gradients -- it's just less distracting.
These things are all true. But a simple layout may not be 'distracting' in the form of gradients, it can be further more distracting in the use redundant JS effects and AJAX (which is a tool, not a method of building sites) and create a whole new distraction that is browsing speed and performance.
Well... with web designs... you don't necessarily make a complete mock-up of what the page will look like. You make enough of it to use when you slice it. As I'll destroy this PSD into tiny pieces to use in the CSS and main HTML, adding content, icons, etc later.