I've had a Merlin Taiga since about 1995/96, (and until 2007 it was my only mountain bike). It's still going strong after 13 years now and 4 summer trips to the Alps, a couple of weeks in the Rockies, and countless outings in North Wales and Scotlend. All the components have changed over the years apart from the CK headset and Royce BB. Considering all the abuse it's had the frame still looks very good and would probably be pretty much immaculate if I gave it a rub with some scotchbrite and got some new transfers.
In 2007 I took the plunge and bought a FS. After much deliberating I bought a Merlin Works 4.0. Love it. So much more comfortable but no loss of trail feedback (it's only got 4" of travel). I can now ride all day with no backache, and as I head towards 40 that's quite a big consideration for me. Amazingly it's no heavier than the Taiga.
Also bought a Merlin Extralight road bike in 2003, no plans to change this either.
I've owned plenty of non-ti frames in the past, but would never go back. I think the big benefit of ti is it's longevity not really the "ride". Sure you can still break them, but some (Litespeed & Merlin) have lifetime warranties for the original purchaser, and yes I do know people who have had successful claims under these arrangements. Being unpainted means there's nothing to chip or scratch and if you hang on to your frames as I do then they do represent good value for money. Although recent price increases have pushed some of them beyond the realm of silly money.