I have one in my camera bag and I love it, for the money it was easily the best lens available however the one thing that does let it down is the slow and noisy AF. For most applications this isn't a problem but I could see it being an issue with a fast moving rally car unless of course you are pre focussing on a set point. For a fast action lens of a similar spec on a budget have a look at the 70-210 f3.5-4.5 it's very similar to the F4 model but has USM so focuses quickly and quietly, obviously it costs more!