Hey Doug,
To me, it all depends on if you're keeping the CD's or not. If you're keeping them, then import however small you feel you need to... you can always fix it later if you want to.
However, I converted my entire library a couple years ago, and sold off the CDs, and to me, there was no way I was going to save that music anything less than lossless. Frankly, hard drive space these days is so cheap, that it's not really a big deal... I had around 1500 CDs whic, in lossless format take up between 250 and 300 GB of storage. I bought a good firewire external drive and use it to keep all my music and photography work, and was money well spent (I actually bought two, with one of them now living in my car, getting syncd up weekly... acting as an offsite backup).
So for daily listening (running my music through my computer, wirelessly to an Apple Express with optical inputs into my stereo) I am using the lossless. I keep a separate library of the exact same music, but saved at AAC 224 - for my ipod. I did some listening tests, both with good headphones and through my stereo, and that is the point where I felt like I wasn't missing too much in terms of the highs and the details, but was also getting a good return in terms of file sizes that 250 + gb fits on my 60 gb ipod with a little room left for episodes of Battlestar Galactica, for when I'm on a plane here or there).
To me, playing music through a somewhat good stereo system, I prefer to have it be as clean as possible... lossless files and a digital/optical input to the stereo... that gives me better sound than my older set up with the CD players hooked up through RCA cables, and like I said, I feel like the cost of hard drives is cheap enough that having songs be around 30 mb each isn't a big deal. If you feel like you can't afford that hard drive space, and dont' want to purchase an external, then I recommend just taking a couple of your favorite songs, converting them at a few different bit rates, and deciding where the right trade off is for you. I expect that pretty much everyone is going to have different feelings about that...
Good luck!
Stephen