I have been running LR for my main workflow since February this year and love it as a single tool that lets me do everything I want. It does frustrate me in a number of areas, including a number of niggling bugs. I have upgraded to LR2.1 RC, and while that fixes some bugs, in introduced others.
My biggest frustration, however, is the raw conversion, or more accurately, the default conversion. I am able to adjust my raw images using presets and other minor adjustments to get them looking the way I want, but by default I often have no idea how the image should look. I realised this quite early and shoot raw+JPEG so I can use the JPEG as a reference. I stack the images after import so that the JPEG is on top and do all my reviewing, etc. with the JPEG. Once I have selected the images to process, I unstack those images and work on the raw files.
One annoying new bug in 2.1 relates to unstacking. With LR1.4, I unstacked using the "S" key in grid mode in the Library. This would keep the .JPG and .NEF selected so I could update the metadata for both. With LR2.1 RC, it doesn't so I now have to make an extra keystroke or so, to reselect both images.
The other annoying bug I mentioned above where LR incorrectly interprets a standard Windows keystroke as if it was directed to LR. I have never seen another Windows application make that mistake.
I have submitted bit bugs to Adobe. I have also put in a feature request to allow the embedded JPEG in a raw file to be displayed for review (which would mean I don't need to shoot the JPEG).