The XPS 13 looks great, but just to address what you said earlier, it's really not going to be much faster than a loaded Macbook Air. A 13.3" MBA Haswell i7/8GB/512GB is about the same speed CPU, and probably faster SSD (PCIe-based).
Not trying to push you into a Macbook Air (screen is outdated, think it might be alittle bigger/heavier than the XPS), but if you find the system specs lacking, not sure an XPS is going to help you. The reality is, you're not going to find a "no-compromise" CPU in an ultrabook. You might be really wanting a 28W TDP laptop instead, which is going to be a bit bigger/heavier. An i7-4578U (like in a maxed out Macbook Pro) at least has a fighting chance to equal the Sandy Bridge mobile quad-core in your W520.
Not trying to push you into a Macbook Air (screen is outdated, think it might be alittle bigger/heavier than the XPS), but if you find the system specs lacking, not sure an XPS is going to help you. The reality is, you're not going to find a "no-compromise" CPU in an ultrabook. You might be really wanting a 28W TDP laptop instead, which is going to be a bit bigger/heavier. An i7-4578U (like in a maxed out Macbook Pro) at least has a fighting chance to equal the Sandy Bridge mobile quad-core in your W520.
