Newbie buying from Best Buy with 15% bonus back— good idea?

Rakuten is offering 15% back bonus at Best Buy and I want to get a $2000 printer. Reading the Rakuten website it sounds like I have to sign up at Best Buy, or am I getting this wrong? I can't believe it, is there some sort of catch?

Also, I see a lot of complaints online about accounts getting terminated before payout, customer support not helping, etc. Do they actually pay out most people most purchases?