I have tried Conversion Optimizer for a while, the first month, i get more conversions. I am not sure if these converions were taken by Conversion Optimizer or just because it's Dec, for people shopping more during that time. However, these two months, i got less impressions and clicks. CTR decreas a litte bit. One possible reason is that there are more competitors. I am wondering if i should manage bid by myself? Since i have used Conversion Optimizer, i have bid the CPA from $10 to $20. So, is it possible that Conversion Optimizer automatically determine whether displays my ads when a keyword triggered. That's why i got less impressions? Do you guys use Conversion Optimizer?
Use better split test of your ads. Launch two ads for each group, after 50 clicks delete the worst ad and make new one. It always helps to keep CTR