SexyAds has been in existence since 1997. Its members are mostly in the US, but it also has a contingent from every corner of the British empire. It is diverse, catering to single, married, and couples, straight, gay and trans, and everything from "penpals only" to BDSM. Fortunately, it has excellent search filters that let you focus on your own particular quest. The average member age is probably around 40. Whether that's good or bad will depend on what you're seeking. This is not the place to troll for young hotties. Billing is through CCbill, a biller with straightforward, no-tricks cancellations.
The site is full featured, with unlimited public and private photos, chat rooms, blogs, member videos, overt or covert profile viewing, a Facebook-style friends/comments page, and the aforementioned search filters. It uses check boxes to construct the basic profile, but encourages the creation of an "ad" to provide a unique narrative. You can search profiles, or browse ads, which is at first confusing. It's similar to doing a search or doing a category browse in eBay - two ways to get to the same place.
After spending a fairly active month on the site, I am convinced that it is completely scam-free. No fake profiles or come-on emails. I didn't get any dates, but I did get a few cordial replies from women who had obviously read my message and profile, and a respectable number of profile views. The site's weaknesses are that it doesn't have a huge membership and is cluttered with inactive profiles.
You can get a very good feel for the site without a paid membership. Profiles are fully visible, you just can't send mail or use some advanced features. But don't try to hide your email address in your ad. I got a very quick note from the site's housemother, saying that I should be ashamed of myself for trying to cheat an honest website. My bad.
It's definitely worth checking out if you fit its more mature demographic. I found it quite refreshing after all the scam sites I had browsed on.