I don't know about him at all but I have seen how the online left reacted to him... surprisngly positive. I'm sure you've seen what Eboue and me (like other lefitsts) think of centrist Dems, so that surprised me. He hasn't really committed to a centre or left program, so I think the reason the left likes him is because he has some innate charm, has been campaigning extremely hard, and because it's Texas, and even a centrist would be a massive step up from Cruz.
That said, Doug Jones, campaigning against the alleged paedeophile Roy Moore last year, campaigned on a decent centre-left hybrid platform but has voted with Trump 60% of the time, which is amazingly bad and a cautionary tale.