Surface mini has 240 ppi screen
7,5 inch at 1440x1080 px ~= 240 ppi. It's more than on Surface 2 / Pro 2 (208 ppi).
It's exactly in the middle between iPad mini and iPad mini retina (1024×768 pixels at 163 ppi vs 2048×1536 pixels at 326 ppi).
What does it mean? Good? Bad? Neutral?
For me it's more than enough and perfect res for good scaling:
To ensure comfortable touch targets a Windows PC needs a maximum DPI of ~140.
The Windows Metro UI support scaling of 100% (i.e. not scaled), 140% and 180%.
A 7.5" 1440×1080 screen scaled at 180% has a effective resolution at 133 DPI.
A higher resolution would result in touch targets that are too small (e.g. 7.5" 1920×1440 screen scaled at 180% would be 177 DPI – way to small).
In my opinion every choice for Surface line is well thought out. Good enough PPI and increased battery life. What do you think? I almost hear the vocal minority claiming it's "shitty, non-retina resolution, good for 2012 but not for 2014".