My first impressions? They are visible right on the tips of my left-hand fingers: every time I practice there are grooves where I've been pushing down the strings. This is week four. My left thumb has stopped hurting, probably - hopefully - a sign that I'm developing muscles in my left hand to finger the strings.
About that bow: you have to hold it just so. You have to move it perpendicularly to the strings, and steer it so that it stays on the "sweet" spot, between the fingerboard and the bridge. You have to press it down hard enough, but not too hard, which has its own unpleasant side effects. And by the way, you have to avoid bowing two strings at once.
Oh, and while you're worrying about all that, you also have to finger the fretless fingerboard to produce notes that actually fall on the scale. The cello has thin pieces of tape on the neck, put there by my teacher for CelloPlayer, as guides for where to put the fingers - thank goodness CelloPlayer has yet to advance beyond those - but they're only a guide, you still basically get to listen to what you're doing. And of course, if you don't press down hard enough, it's still no good, even if you do hit the perfect spot.
In short, for multi-tasking, this is the hardest thing I've done since learning to drive a car with a shift stick, back when I was a teenager.
But I love it. And on those occasions that I manage to do everything right at once, the cello rings with a full, clear sound, filling the room, reverberating against my body, and making me immensely happy.