I was lucky enough early last year to pick up a Genesis Altitude Ti frame cheap 2nd hand in my size. Now the benefit for me here was I already knew how the 853 steel version of the same frame rode, as I'd already had one for 2 years and loved it. I've ridden Ti frames in the past that I've not got on with at all well though (usually too flexy, notable exception the Cove Hummer which was lovely!) so didn't immediately sell the steel version.
Anyway, said I'd keep the steel frame 6 months in case I didn't get on with the Ti version. 3 months later, it was in the classifieds on here. I love the Ti version even more, it's got all the great characteristics of the Steel version (which is probably 99% down to the geometry), but it's almost 1.5lb lighter, it's definitely slightly more forgiving over a longer ride, and it doesn't have any paint to chip or scuff!
Like I said though, there are plenty of duff Ti frames out there, a wonder material cannot fix poor geometry or bad design, but IMO it is possible to make a great frame even better (at significant cost of course) if you make it out of Ti. And I was the world's biggest Ti sceptic for years, and to be quite frank I'd still recommend Steel and a whole heap of cash in your bank balance over Ti to most people, but if you know what you like and you've got the cash burning a whole in your pocket... Then why not! It's totally unjustifiable (unless you're paying as little as I did 2nd hand), but it can be bloody marvellous!