The one handed access was a big deal for me. I really hate things on my belt, so it was "a leatherman type tool, or a knife", with the knife being the default, and the most important function on the multi-tool
I did NOT get to buy a Ti - the 154CM blade wasn't enough incentive to upgrade from my existing leathermen (yes I had plenty) but I did use a friends Ti for a week.
When the TTi came out, I decided "what the heck, I'll give another one a try" That and the fact that I was threated with arrest for carrying a Leek ("That's a switchblade" - yeah I know that it isn't, the courts know it isn't, but it's not fun having to prove it in a court of law), so I was looking for "yet another knife"
The TTi was the first multitool that was "good enough" to displace my folder to a backpack. The file on mine stinks - it was miscut, and they have offered to replace it, but I've seen ones that are cut RIGHT, and they still are not very good
If and when I get a surface grinder (on my wish list), I may take a gobert flat file and grind it down in thickness, and shape it to replace the existing file. I did ask Leatherman about "do a super tool with a real file, a real blade, say D2, etc etc" and their comment was that there would NOT be enough of a market, that the lack of rust resistance would be a deal breaker