Cougarlife.com is an established and reputable age gap dating site. I'd not use it if you are just looking for casual encounters. For that purpose you can easily find women on Cougars69.com but if you are seeking a serious relationship with women in their 40s you can't go wrong using this site.
I would not really pay attention to the negative reviews. They are comprehensible sometimes but often those guys complain which used this site with wrong expectations.
Only CON I see are the credit based high costs. It gets quiet expensive but may be worth it.
Conclusion: Do not use if you just want to have a casual encounter. There are better sites for this purpose. But if you are looking for a serious relationship with an attractive woman in her 40s Cougarlife.com will give you what you are searching for