I think the 350/650 series of readers were the pinnacle of readers. It's been all downhill from there. The 650 is my main reader (I really do need the extra inch of screen) but I have the 350 as an extra/spare. Actually I have two 350's but I seem to have misplaced one of them. Very irritating since it was misplaced with a cover. The covers are much harder to find than the readers.
PRS+ is a huge improvement over the Sony software. Sony has never, ever produced software that did not massively suck. Their SonicStage comes to mind (and remains embedded like a shard of glass.) The T1 was a real disappointment. The users interface is worse that the stock 650 and only function of the wireless capability is to turn it into a point of sale terminal for the reader store. The Kobo mini has the same problem except that it shills for Kobo. The T1 also shills for Google but Goggle doesn't sell to Canadian readers.
The 350/650 readers are just that, damn good readers.