Right, three things.
First and foremost: yes, once you rip things lossless, you never have to touch the CDs again. Far as I'm concerned, that's the whole point.
Second, on my version of itunes, when you plug an ipod in, and you then select it from the menu on the left, you get the screen with various tab-like choices on the top to manage what's on the thing ("Summary, Apps, Movies, TV.".. etc.) On the "Summary" tab, there are three areas ("ipod" "version" "options") and the third "option" is "convert higher bit rate songs to 128 kbps AAC." If you select that, it's precisely what it'll do for you when you sync. No fuss, no muss, and a full ipod.
Third, our genuine Remo is of course correct, if you want full auto, 128 kbps AAC is your only option. Typical Apple: you want it easy, it's our way or not at all. But, you can also get itunes to manually make you a copy of any track you want in any other format that itunes supports (AAC, mp3, AIFF, Apple Lossless, WAV -- basically anything but FLAC). How to do this, however, aint obvious.
The itunes "help" file explains it thusly:
To convert a songs file format:
Choose iTunes > Preferences, click General, and click Import Settings.
In the Import Using pop-up menu, choose the format you want to convert songs to, and click OK to save the settings.
Select one or more songs in your library and choose Advanced > Create [Format] Version.
In the off chance that this made no sense at all, it kinda goes like this. Both in your "Advanced" pull-down menu and in the right click menue for any given track, you will be presented with the option to "Create [blank] Version", where [blank] is the default import setting. In other words, if your default setting is to import AIFF, and you have just ripped your entire library AIFF, this option will very helpfully (and apparently without a touch or irony) give you the opportunity to make another AIFF copy. Lovely.
BUT, and I suspect you may see where this is going, if you change your import preferences (say to whatever bit rate mp3 floats your boat), then this same right click / "advanced" option will then the present you with the ability to make a copy in whatever your new default is. You can then select your entire library (or as many or few tracks as you like) and make a copy of all of it in whatever format you want (just remember to switch your default back before ripping any more CDs, or that's what you'll get from them as well).
To sum up, the Apple way is either their way or the hard way -- but you can usually get the job done.... Personally, I like the easy way (think it's spelled l.a.z.y.), but also because I am fanatical about best possible quality on the full rig, but neither care about nor appreciate any difference once it goes on the ipod. But, if your ears and/or the gear you run the ipad through appreciate the benefit of higher bit rate lossy-ness (and I won't pretend that's a particularly difficult task) then you're stuck doing it the hard way and juggling multiple copies of each track in different formats. Enjoy, and as long as you do, you're of course doing it just right.