anyone used first response opk's?

Hi all, I had to switch brands mid cycle, I ran out of lullaby opks and had to buy first response from woolies. I usually have a hard time getting a positive result with any brand. Has anyone used first response and can you recommend them>??
I think they were positive, so close to being positive but wasnt 100% sure. The second line was dark enough that it was hard to be clear which was darker so i say positive.
The reason I ask is that I do not normally get a really strong positive, just almost positives with lullaby's so I am a little skeptical of the new brand. Such a pain having to change brands right around O time.
Any hints or ideas?
ta, sassba.