I have a Canon 1.4x, it works great for me. Sure, you lose some image quality, but I find it's much better than trying to crop when you're a little on the short end of the spectrum. It does suck if you're shooting past dusk, and I tend to remove the extender during those times, but luckily, that's usually towards the end of the events.
I would NOT suggest going cheap with lenses or extenders. I have had some Sigma lenses in the past, and while they worked alright on lower end bodies, as my photography progressed and I upgraded to higher quality bodies, the flaws became more and more apparent. I now have all Canon gear, and am much happier with the final product.
Tessa wrote in post #15477927
I shoot motorsports, yet rarely need anything longer than my 70-200. I'm not going to spend thousands on a lens I'll use maybe four or five times a year. So yeah, while extenders are not the best solution, they do have their place.
I shoot 10 or so events a year, and I'd say I use my extender at 6 of the 10.