Simple thread!

Considering buying/renting RAGE, have been doing since I saw a gameplay trailer for it back in June and it looked superb. Since it's come out, I've been hearing a bit of flak regarding its linear-ness, lack of online playability, and more general criticisms that I'm not entirely sure I agree with.
Basically, if I rented it from Blockbuster (£5 for 5 days, woo), could I complete it within my rental period? If not, should i buy it now, or wait until the sales chop it down to <£20?