Thanks guys for all the positive comments.
To Mike - The A77 and NEX5n are very different beasts - I love the handling on the a77 (including the portrait grip) and the detail on the a77 can be stunning at low ISOs .. but its very unforgiving in terms of user error in terms of handshake, slightly off exposure etc - and the noise creeps in very quickly, even at iso 800. Also, its pretty big and obvious as cameras go so not a great discrete street camera. By contrast, the NEX5n still feels a just little difficult to control
quickly despite all the customisation options but so far the resolution is more than good enough and noise control seems superb with the possibility of getting even better - I tend to use DXO for raw processing and at the moment it has no preset support for the 50mm or the 2 sigma lenses, so I'm lazily using my a77 user presets to process the images - they are probably a bit heavy handed for the low noise images the nex outputs. When I get some time I'll sit down and make some new presets for the new NEX lenses (and hassle DXO for more lens support

and play around in lightroom to see what works best.
But overall, I'ne very happy with the 5n so far - the handling feels better than my old nex 3 (e.g. the touch screen focussing has been genuinely useful and I've assigned ael toggle to one of the soft buttons, an arrangement that quickly lets me set focus point and exposure in A and S mode) and the raw images coming off the SD card are pretty amazing for such a small and compact camera... now if it just had one more control dial (or there was a NEX 6 for less than the 7 with the body of the 7 but the 16MP sensor)... oh and if Sony could just squeeze in the stabilisation back onto the sensor like the alphas that would be swell.. and more pancake lenses... etc etc

. I'm joking (sort of) - I'm very pleased with the 5n - its not as sexy as the 7 but its a great camera and great value for money at the moment (readily available for 450 GBP or less if you include the cash back deal here in the UK).