I went through this last season. I rode the sled with it "deleted" (more on why I put that in quotes below), not deleted, stock suspension and aftermarket suspension.
First things first, a lot of those deleting T-Motion are only limiting it. The washers still allow more flex than say an Axys. The whole entire skid (from track to the metal bits) has a fair amount of flex built in even with washers installed.
Second, everyone thinks they are Chris Burandt. Be honest with how you really ride. Be honest with the style of riding you really do. Yes, the steeper terrain (and harder the snow) the more the washers (or better, a pure delete) help *if* you are sidehilling.
Third, there are 100% places where an articulating skid is awesome. There are places its not so awesome. There is no free lunch. This is why the hill climb guys generally like it, it helps keep track on the snow and actually makes the ride smoother.
Fourth, predictability while crossing tracks has more to do with the way the ski doo is incredibly ski-heavy (and the crap stock shocks) than it does T-Motion
In the end, the power of placebo is strong. If you believe something is better, it usually is. I didn't find the sled was massively different with the washers in, but I preferred it. Other forms of lockout I tried from Tom (after I put his kit in) were preferred by me as well, but there is a lot more going on with that sled that I think contributes to the ill handling everyone talks about. Addressing these issues yields better handling than deleting/leaving T-Motion.
Someone here said "just get used to it" and I think that is some sound advice. On the other hand, washers are $50. Give them a go if you want to firm things up a bit. The skid will still flex a fair amount (especially with the track).