I own a Sony M10. The built-in mics have excellent self-noise, which is of primary importance for ambience or most wildlife recording. However their soundstage is terrible, not surprising considering how close the omni caps have been placed. I cannot easily enjoy any recordings made using them. The solution is external microphones. And yes, it is true that this model has been discontinued.
Someone above mentioned the Olympus LS series of recorders, which are indeed my favourites. I own the LS-10 and LS-11. There's also the LS-5 in this line, and the only significant difference is how much internal memory they have, and the packaged accessories. There was a bass roll-off issue with the LS-10, but TBH it never bothered me as I was likely to do this in post anyway. Unfortunately these too have been discontinued.
Do not confuse these with the LS-12 and LS-14, which have plastic build and poorer, though still very good, pre-amps. Yes, I've got one of these too! They are excellent units for beginners, due to the Quick Mode recording setting. I first took this for a gimmick but it really helps setting record levels. Also, they sell cheaper than the discontinued models used to.
Forget the Olympus LS-3 and LS-7 which are tiny but more noise again.