I used the last beta and the trial for some time and recently I bought the final version. I've did some tests with other candidates (Bibble, Lighzone, C1, SilkyPix, RawShooter, DxO (with converted TIFFs) and the free RawTherapee). I mostly looked at the details each of the packages was able to pull out from the R-D1 files and my impression is, that Lightroom and RawTherapee gave the best results. The reason for this maybe that both use the code of dcraw to convert RAW data (at least RawTherapee does, for LR I'm not sure) and this little commandline tool is astonishing regarding image quality.
If I find enough time I'll post some results in the forum (they will only be based on results achieved with R-D1 files).
Apart from that LR does it for me. It has an elegent UI, quick to use; image correction features are very good, fine grained and well designed and the database features are sufficient for my tasks. I also very much like being able to do an ad-hoc slideshow.
For me it is also nearly feature complete. Nevertheless LR has also weaknesses, for example the before mentioned limited sharpening capabilities. But that maybe solved by plugin vendors in the near future when the SDK will become available. As a PC user I can't speak for Aperture but among the other software I looked to, LR was the most comprehensive solution. I personally can recommend it very much.
Sure, for some tasks a dedicated image editor like Photoshop is better suited or necessary, but these pure editors mostly will lack the workflow functions of RAW editors.