Every time I conduct an interview, I try to get it recorded.  I have tried out several high-end recorders, only to find out the are "too good."  Too many times when I have used the high end products, they are too sensitive and pick up way too much background noise.  When I say recorders - I am speaking of digital recorders.  I do not use tape any longer - it is just logistically too impractical.  The 4th recorder I decided to try out was basically out of need.  I had sent back another expensive model, and I needed one as a stop-gap measure.   I bought a $59 model from Wal~Mart.
The recorder I got was a Sony ICD-PX312 digital recorder.  It has a removable micro-SD card (which was one of the few requirements I have).  It can record in several formats, and has several quality settings.  I stated off using everything in the middle range.  It it easy to set up and easy to use.  I can turn the recorder on and lock the power button so it continually records conversations.  I put the recorder in my pocket and conduct the interview.  It doesn't matter if it is a shirt or pants pocket - it records the conversation really well.
I would have to give this recorder a 5 out of 5 rating if I had a system.  It is easy to use, easy to set up and always gives me a great recording.  This equipment is standard issue for everyone working for me.
If you use something that works really well, I would like to hear from you.