Have to say, on the few occasions I've travelled on a 323 I've not thought much of them at all. Uncomfortable, poorly looked after, and that whining noise is horrific. Better than a 150 for sure, but I'd take a 319 any day.
From what's said, I assume we're expecting to see them on the Lime Street - Preston via Wigan (and thence onto Blackpool) service that's currently 319 worked. If so, I hope they get at least a cosmetic refurb and better seats first, because otherwise they'll appear to be quite a step down from the refurbished 319s. Rather than being praised as 'not a cast off' I can see a fair few people travelling Wigan-Liverpool being decidedly unimpressed at a not very well looked after Northern 323 turning up in place of a shiny white 319.
On another topic, are they (or will they be) cleared over Chat Moss? (ie. between Manchester and Golborne Junction)