Pictor - I felt the same way about Silver Efex relative to Aperture. But I did the trial version of Silver Efex and came to like it a lot. Technically, I could end up with pretty close to the same results with Aperture as with Silver Efex. But once I got competent with Silver Efex, I'd process a given RAW file with both the tools within Aperture (including a bunch of presets for various film types, effects, etc) and with Silver Efex. And almost without exception, I liked what I came up with in Silver Efex more. Once I had a Silver Efex version I liked, I would sit there and play with the adjustments in Aperture and could eventually get pretty close to the same results, but it took a while and I'd have never gotten to the same place just using Aperture. I also really like the way the tools in Silver Efex work - they're so geared to working with B&W that they just fall right into place. So I had VERY similar feelings to yours, but experience changed my mind and now I use Silver Efex for almost everything (although I still have a couple of IR presets in Aperture that I occasionally prefer to the IR results I can get out of Silver Efex, so I still use those occasionally). The other thing is I can't control grain in Aperture and I can control it down to the last detail in Silver Efex - I don't know if this is true of LR as well, but for me this alone was nearly enough reason to buy it.
There is one big downside to Silver Efex, relative to either LR or Aperture. Which is the programs creates a TIFF file to work from rather than working directly from the RAW file and just saving a group of settings as a given "version" (not sure if LR uses the same nomenclature but I think the basic process is the same as Aperture). These TIFF files are huge, 5-6 times the size of the original RAW file. And once you've worked on it in Silver Efex and then hit "save", its fully cooked. You can't really go back in and edit what you've done except in VERY limited ways. So its not always a live version, as anything in Aperture or LR are. So the workflow and file situation is a bit of a downside. Once the TIFF file has been processed to my satisfaction, I always save it to a JPEG and then trash the TIFF because a typical full size jpeg is maybe 3-4 megabytes, the original RAW is around 12-15 megs, and the TIFF is up around 60+ megs. Since the file is basically finished once you save it, no reason to hold onto all of those huge TIFF files.
There are definitely downsides to using Silver Efex rather than just LR, but there are upsides as well. After using it a while, I found the upsides much bigger than the downsides. Its at least worth working with the demo for a couple of weeks to see what you think...
-Ray