I have a good friend that has two - a standard ti (made by merlin) and a travel extralight (merlin also) with the fittings that let you take the frame apart (the name of those couplings escapes me). The latter is actually stiffer as the couplings stiffen up the frame. He's had them for about 12 and 10 years respectively as he got the standard one before the travel one. He raced 4s and now 3s and is reasonably happy with them. Another friend has a standard ti and finally someone (I think the second one's wife) has a steel Spectrum or two.
As far as feedback goes, they're very good quality. Since the Ti frames were essentially outsourced to Merlin (and then finished by Spectrum), it's hard to say anything about them other than they're nicely finished merlins.
The one that has two ti frames is thinking of updating his frame/s. He doesn't have an unusual fit so he'll fit a number of frames out there. I suppose this desire to update is normal for a rider who competes and who has seen (race) bikes go from 22 lbs to 15 lbs. He's willing to use the latest and greatest equipment as he uses Campy Record 10s, SRM cranks, Zipp 404s or Campy Eurus wheels, and has two TT bikes.
cdr