I believe that the most important service that a wedding planner can provide is to be an insurance policy for the wedding day. If something goes awry, the planner is there to make sure no one, especially those getting married, notices a thing.... Secondary to that, vendor contacts, recommendations, and design assistance also provide a great deal of value.
My wife and I were married in March 2014. Prior to selecting Barbara, we had identified our major vendors already (venue/catering, cake, photographer, DJ). We used Barbara's list of selected vendors to identify stationary, a florist, and makeup/hair stylists. We had no issues with those vendors; they performed admirably. Many of the vendors we selected ourselves already knew Barbara and commented on how well regarded she is. During our initial meeting, she took copious notes on what we had accomplished up to that point.
During the lead up to the wedding, I had also devised a post-ceremony surprise for my wife that required Barbara's help to coordinate and to maintain the surprise for her. Honestly, I couldn't have pulled this off without her help. (However, one small knock is that it almost didn't happen because of an over-reliance on email, without a phone follow-up, between the parties involved. Fortunately, all was well in the end.)
Going into the event, we had a budget and design thoughts in mind and presented them to Barbara at our initial meetings. While I never considered the budget a firm limit (especially when surprises are being coordinated in the background), I do think it was generally respected during design meetings. A few times, my wife and I had to scale back some design elements, and those decisions were respected and accommodated well. (Not surprisingly, unless you have everything settled for your design beforehand, a designer has lots of ideas about what you'll "need" for your wedding (e.g. chair covers, fancy layout for escort cards, etc.), and those elements get discussed or tossed in by default. This was true here, but as I mentioned, we didn't encounter resistance from her or her vendors when we backed those items out.)
During the wedding day itself, neither my bride nor myself were aware of any issues arising. In fact, guests commented on how flawless the day seemed to go, which is an oddity these days given how complicated weddings seem to be. While we had an impressive set of vendors that might have functioned well enough with the venue, I believe having Barbara there improved our odds and was an invaluable asset, contributing to the smoothness of the day. There was one potential weather-related hiccup with the planned surprise that Barbara was able to handle without any involvement from me and to my satisfaction. We felt very well taken care of as we were ushered from one point to another in the maelstrom that surrounds every couple on their wedding day.
All told, we had a spectacular event, and it would not have been the same without her assistance. I chose 4 stars on service because we felt she had an assumption that we'd let her know if we needed her for something. While we were pretty self-sufficient in many ways, some proactive queries on how things were going and if she could help us with anything would have been well received. In all fairness, when we did reach out to her, she was available and able to help with questions. If top quality and value are measured by flawlessness during the event, then 5 stars is easy.