There is specific flexibility that you should focus on for the OLs that will work faster than yoga.
If you want yoga for some relaxation, go for it. If you have focused goals you want from your flexibility regimen, go after those.
Greg Everett wrote some great articles on flexibility in the earlier PMenu issue, you might want to look them up.
I have plenty of flexibility for the OLs, I'm hoping to get in one yoga class a week now, mainly for the relaxation (and I can always use more hamstring stretching!).