I have an XPS 15 (>2 years old) and also had battery swell, which made the trackpad unusable along with other safety concerns. Dell decided to replace the batteries for the 84wh model for free, but not for the 56wh model, which is very disappointing...
Also the throttling in the XPS 15 is real. Even with the 960m I can't even run light games on it because of frequent fps drops... And the BIOS was pretty unstable for the first year (laptop running fans at maximum while in sleep mode, while getting really hot inside my bag), with lots of coil whine. Overall, I am very disappointed in the overall build quality of it (I previously had a 2010 macbook pro and had no problems). Going to try a Lenovo for my next laptop (it seems to have less build quality issues)