Basically, it carries all the sides of excessive testosterone levels. Androgenic side effects - acne, hairloss (if youre prone to it) can be expected. As well as side effects of aromatization - bloat, water retention, gyno.
Keep in mind though that the sides are very dose dependent. You might not even feel anything at 500 iu/2x weekly, but at 2500 iu and over it will be pretty noticeable.