I spent one week in SSRC with my family (2 adults, 2 children) in August 2014. It is important to separate the property from the units, since some of them are rented privately and some are rented through the property management company. I would suggest you go with the managed units, if you do so then the desk can help you if problems would arise. Secondly, do your research on their website about each unit: there are great differences in beds, amenities such as TVs and overall furniture and unit decor. I will divide my review in two: first the property, then the unit.
The property is extremely well kept: clean everywhere, plants well tended, pool clean, chairs available all the time, free and fully functional wi-fi, security present but not oppressive (we were in low season, though, and they did not require us to wear wrist bands), tennis fields free and racquets/balls also available at the desk, grills working, parking spots largely available; in summary, all that was described on the website was there and perfect. I did a lot of research and not all properties on Siesta Key offer such amenities, and even if you may have to pay a little more, in my opinion it is worth it.
Our unit was W0205: we chose building W being close to the beach but not too close where the noise from the gazebo/beach would reach us. Second floor in my opinion is better, first floor gives less privacy. Our unit was clean with large supply of towels and well equipped kitchen. The bedrooms were as described and bathrooms were large and clean. All appliances worked well, the towels were changed once mid-week. Minor negative points would only be that the sofas in the living room were a little dated (the cloth felt a little used) and the area rugs at the entrance and in the corridor also felt heavily 'used'. Apart from that, the unit was fully functional for our needs and we cooked 2/3 meals a day in the kitchen with no problems.
Overall, SSRC is one of the best options for a Siesta Key vacation and we will be happy to return again.