At the risk of talking about the company I work for a bit too much, allow me to shine some light on Meguiar's Ultimate Black:

First off, it's a water based dressing not unlike so many others on the market, but it does contain some specific polymers that allow it to bond to plastic and vinyl surfaces in much the same way polymer sealants bond to your paint. Where most other water based products will wash away when they get wet (washing, heavy rain) this one tends to stay put much better due to this polymer load. The trick is to apply it to a surface that does not have a heavy load of another product already on it since that can compromise UB's ability to bond. This is especially true if you've used a synthetic polymer product on the surface previously. For example, Meguiar's Ultimate Quik Wax, which is a spray wax that won't stain plastic trim; if you've used UQW on your trim and then try to apply UB over it, the UB won't bond and it will wash away pretty quickly. In live2drive's case here, where he applied it to a dull, dirty and definitely in need of TLC piece, he's likely going to get the most out of this product.

Application is important, too: don't over use it, and really work it into the surface. A little bit goes a long way, and if you have any excess product to wipe off after applying it, you've used way too much. It should dry completely dry to the touch in a matter of minutes.

That said, there's plenty of great stuff on the market for this application - Black Wow, Solution Finish, and some of the new silica glass coatings from CarPro and others (although those are really pricey). My recommendation is always to find something you like and use it regularly. It's always much easier to do maintenance work than restoration work, so staying on top of things takes just a few minutes and keeps things looking great all the time.