For ATT U-verse Internet only, it seems that there will be a $2 equipment fee. »High Speed Internet Equipment Fee 2.00
I have the 18/1.5 U-verse. It is peppy. It has low jitter (pingtest.net) I am confident that the 12/1.5 plan would be very peppy too for me since I am not downloading a lot of stuff. If I were streaming a lot of video, the higher download speed would be important.
I don't get packet loss. That is an important factor in performance.
If you stick with WOW, buy a DOCSIS modem and turn in the modem that you rent for almost $7 per month. Get a receipt when you turn in the rented modem. If they are not using DOCSIS 3, you can probably find a good deal on a used modem.