Biased here, but Redgate SQL Backup works really well. The speed gains are mostly from compression, which is what many of these products use.

I am wary of products that don't simulate and record their backup in msdb just like a native one. Anything that pretends to snapshot files is worrisome. For those that sit on top of native backup and offer compression, they all mostly work the same, just with different tuning options and multi-server support. I'd test a few.

Disclosure: I work for Redgate.