In theory, a 16-bit TIFF should be able to hold all the same tonal information as the original raw file, but you'll be losing the ability to reprocess the sensor data later if you run across an image that responds better to a different raw-file converter. (That's not a big factor if you never do this, though.)
You could get around that risk by archiving the original raw file along with your TIFF, but eventually that would amount to a lot of files. For that matter, another disadvantage of this method is that the TIFF will be somewhat bigger than the original raw file.
Still, it seems to be the only way to work with Aperture if you use an R-D 1. If you do try this, I'd like to hear what you think of how it works in practice. I too have been using Lightroom B3, and it's okay (and a big improvement over the previous betas) but it doesn't have anything close to Aperture's tools for comparing and selecting the best shots from a session, which is by far the most time-consuming part of my work process.
(There's also the interesting conundrum of what Adobe's eventually going to charge for Lightroom. So far everyone playing with the beta seems to assume that it's going to be less than Aperture, although Apple's price cut on Aperture would put a lot of pressure on that. Suppose Adobe's strategy is to get people addicted to the beta, with a lot of time invested in building libraries and applying adjustments to images, and then come back and price the final product at, say, $795? In effect, Adobe would be holding your work hostage: Once your beta expires, you'd either have to cough up the asking price or give up all the time you had invested in your image libraries.)
