After a year of T350 ownership I would say two things:
1) Yep, they can be as problematic as the rumours suggest, but...
2) If you go into ownership with your eyes wide open, and are prepared for the occasional trip back to the dealers, you can forgive them their faults, again and again, the second you sit in it!
In the time I had mine, I had senders replaced (oil temp, water temp, speedo) ... very common problem and a quick / cheap fix. Head gasket went (about a week after I bought it), luckily this was covered under warranty, and then finally the half-time bearing went causing near fatal engine damage - luckily it was diagnosed in time to prevent complete engine faiure, which was imminent! There were a couple of other things too with window electrics etc.
As stated above, these cars actually like to be driven and it's the regularly used cars that seem to be most reliable. Unfortunately mine only came out of the garage every other weekend, and seemed to mysteriously develop faults in the meantime.
Would I return to TVR ownership? Almost definitely yes - I too have a hankering for a Sagaris, and my experience to date has only heightened that.