My desktop performance on both my 32GB Linux desktop at work, and my 8GB Windows desktop at home is generally flawless, and I rarely have fewer than 10 tabs open in either place. I do use Chrome exclusively; maybe the performance in another browser is a different story? I assume Chrome's process-per-tab design would make this experience a little more robust.
Secondly, did you try w/ both Flash (the default) and the HTML5 player? You can enable the HTML5 player in the Labs section of Music; that might significantly alter your web experience.
Yea, I've tried both the Flash and HTML5 player, and I don't think I noticed much difference. And this is all using Chrome as well. Also, I notice the skipping not just when something intensive is happening in another tab, but also when another application is doing something heavy. Perhaps it's something on my machines... but whatever it is, it doesn't happen with Spotify's desktop app.
Secondly, did you try w/ both Flash (the default) and the HTML5 player? You can enable the HTML5 player in the Labs section of Music; that might significantly alter your web experience.