Sony Minidisc - need advise

I just need your advise on buying a new portable audio recorder.

About 3 months ago, I bought Olympus DM-20. But this is a very bad
device. Firstly, it does not have on/off button, so as soon as you put
the batteries in, it will remain ON all the time. It records the
audio in a proprietry format. I cannot play my other MP3 on DM-20.

I hoping not to repeat the same mistakes with my new audio recorder.

Somone recommended Sony Minidisc player. But can u tell me if following can be achieved with a minidisc:

(1) I need a small audio recorder that I can put in my pocket and
record the discussions / lectures....

(2) The recorder should be able to record in MP3 or WMA format.

(3) I should be able to put these recording onto my other MP3 players and play them.

(4) I should be able to play my other MP3s on this recorder, as well.

Can I achieve the above with a Sony Minidisc???? Which model should I get?

Any advice??