So far, my son has used it more than I have! LOL He absolutely loves it. I've been using it to listen to podcasts mostly. I do have an Audible.com account, and I've downloaded one book from there (it's a 17 hour long book!), which I was able to put on my Sansa and burn to CDs. My son LOVES audiobooks, so he's in heaven.
The 512 MB MP3 player is more than big enough for me. I accidentally downloaded one of the larger formats for that 17 hour story, and it still took up less than 1/4 of the memory. It doesn't have a bookmark feature, but it does remember where you were in the story. The big problem is, if you accidentally hit the skip forward/back button, you have to fast forward to the spot you were at, and that can go VERY slowly. The podcasts I was listening to weren't split into chapters, so if I accidentally skipped back to the beginning, it might take 10 minutes to get back to my spot. The audiobooks are split up into 5-10 minute long chapters, so it doesn't take nearly as long to find your spot with those.
Roman is kind of rough with it, and he's dropped it more times than I'd like. So far, it still works; although twice, I've had to reload the audio files due to an error. I think the errors were caused by dropping, but that does concern me.
I agree that the headphones it came with aren't the greatest. I'll probably replace them eventually, but they get the job done for now.
BTW, Audible.com has a give-away thing this month, and I get entered to win prizes every time someone uses me as a referral when starting a new account there, so if you're interested, send me a private message, and I'll give you the info.