The Inspiron Mini 10 is pretty much a mixed bag, and although it shows promise and offers a few nice features and design concepts, it has a few serious shortcomings as well.
For some reason Dell chose to launch it with a 3-cell battery, which doesn't provide you with a lot of juice. Most vendors are slowly phasing out 3-cell units in favor of 6-cell or 4-cell batteries, even on entry level SKUs. Of course, you can get a 6-cell power pack for the Mini 10, but you're basically paying for something you are supposed to get straight out of the box, and that's something no consumer enjoys.
In terms of performance, the Z520 is a bit on the slow side, although it can still cope with the typical netbook workload. The upside of using the Atom Z520 and US15W chipset is that the Inspiron Mini stays pretty cool and quiet no matter what you do.