Yea, I sort of see it as being pointless. Me and SO picked out my engagement ring a few weeks ago, and the first ring I looked at, the sales lady was like "Oh, thats a pre-engagement ring." Lol I was like WTF?
If you know you want to marry me, just get a damn engagement ring! Its not like it means you have to get married ASAP anyways. I dont need a promise of commitment to come later, kwim?
I think it depends on the age of the couple. DH gave me a promise ring on our six month dating anniversary. He was 17 and I was 19 (senior in high school and freshman in college). We both knew we were in it for the long haul, but were no where near ready to actually get married. Honestly, it was more romantic than the actual proposal. Fast forward and we've been together 7 years and married for 3.5.
Now, if he had given me a promise ring when we were older and ready to get married, I think it would have been cheesy. It seems like a teenage thing to do. But, to each their own.