Sony had always made solid, but relatively unimpressive ereaders. Back in 2007-2008 when ereaders were just taking off, Sony was a major player. But their lighted ereader, the PRS-700 was horrible. And they do not seem to have recovered since then.
Goodereader has a review (appears to be reviewing the specs and not the device) along with some commentary and quotes. They do not seem to be impressed with the new PRS-T3. And from the specs I can’t imagine many others will be either.
It is not using the newest eink screen, it does not have a lighted display and it is priced at $150. It does come with a thin lighted case. But that does not seem to justify the price to me.
One advantage is that Sony has an exclusive deal with Overdrive (the software that runs most online library lending systems). Sony is the only ereader that directly runs software to borrow from your local library without the use of a computer or browser.