While I generally think it is a good idea for employees to have some job protection when ill, or more importantly to be able to deal with troubling and highly charged and stressful situations such as domestic violence, my concern is with the requirement that it is "paid" time off and applicable to employers with 15 or more employees.
Large employers can certainly handle the law and such expenses. Indeed, many of them already provide similar benefits (although I could easily see larger employers reducing benefits elsewhere to recoup lost revenue created by such a mandate if the employer(s) are not currently offering such a benefit). However, to require a small employer (under 100 employees) to provide paid sick leave, which is presumably above and beyond any paid vacation time already offered, can create a major financial burden for an employer struggling to regain footing in this economy.
Perhaps a better proposal would be to require employers with 100+ employees to provide paid time and smaller employers to only have to provide unpaid sick leave time. This still meets the need for job protection without creating a huge financial burden on small businesses.