Just be sure to keep in mind that with the recent RZ changes, you won't get any RZ points if you use the promo 18 months no interest financing. The other three reasons are good ones, tho!
You will only get points if you choose "standard credit financing", which would only be beneficial if you pay it in full after the charge hits the statement cycle.
Best Buy purchases using standard credit:
Get 2.5 points for every $1 spent (that's 5% back) on qualifying Best Buy purchases on the card using standard credit.
Best Buy purchases using promotional credit:
Purchases made on your credit card using promotional credit do not qualify for points but will continue to count toward My Best Buy Elite and Elite Plus status.