I've also found prints with a bottom detail to be tricky. A lot of things have to be "just right". Concurring with 3DPBuser, bed clearance is critical. Bed needs to be very level if ABL isn't being used. The skirt width seems to vary around your print, or is that just the photo focus? Are you confident in the current extrusion calibration? IIRC Slic3r 0.9.9 tended to under-extrude. How long has it been since any buildup of crud has been cleared out of the nozzle? I have no experience with buildtak, but 3M blue painters tape swabbed with 91% isopropyl alcohol gives me better first layer PLA adhesion than anything else I've tried. By far. I've broken some prints and one glass plate trying to get prints removed from it. Printing onto an unheated bed with the blue tape seems to also give me better bottom-side detail than printing on a heated bed.