I currently have the oc2, ebs, mxr, and dod octoplus.
I've also got the whammy and digitech bsw both of which do a decent octave. I've also used the ehx and Aguilar. However the latter two didn't stand out for me sound wise
It's absolutely crucial to find the one that sits best with your playing in a mix. I spent hours with both the mxr and ebs going head to head. I went with the ebs initially, but found for me that it didn't sit right in my mix. However once I got the mxr it all worked perfectly for me.
The dod and boss have their own distinct and individual sounds and have definite uses for certain genres.
I have to say that I love all of them in differing ways