hi small_dog.
About a year ago I needed a portable for work and after a bit of research came up with the Philips PET720 as meeting all my requirements.
Overall I am happy with it and it hasn't let me down, though the quoted battery times are possibly a bit optimistic - but they probably are for all machines. I reckon I get about three - four hours out of it. It can also work off the mains.
If you run it in battery mode then the battery, which is external and attaches underneath the unit, doesn't fit very securely and is always falling off when being carried by hand (not in a case) so you may need to get some velcro or something else to provide a securer fit.
One bad point is that it didn't come with a case as standard and so you will need to get a case from somewhere else, but be aware that the battery does stick out the back so check that your proposed case will take it with the by now properly secured battery attached.
One advantage of this model is that it does accept an external video input so if necessary you can hook up a camcorder or possibly a video ipod to it using the Philips supplied minijack leads but don't expect to get a very good picture.
I like the push buttons as they have a sure touch to them and have survived well when the unit is used for transcription stop start rewind start rewind start etc. and unlike some other units that I looked at it does appear to be quite hard wearing.
I don't like giving out wholehearted recommendations as it is so subjective but what I will say is that so far in about a year this unit (my first portable DVD) has suited my needs and hasn't gone wrong. (Outside in daylight can sometimes be a problem and lots of papers are needed to shield the screen from the sunshine!)