I've been with Bigpipe for a couple of years now (ADSL), and never had any issues.
Just reviewing plans and it looks like if I switch to Spark I'll get $300 credit + Netflix for 6 months on a 12 month contract, which will save me a reasonable chunk.
Is the likes of bandwidth management (any kind of throttling etc.) any different? I'm not sure if they still do that or not, but I've never had any issues getting as good as could be expected from ADSL with Bigpipe.