I don't have any ti backspacers installed, though I have had an anodized ti backspacer and moved it along to someone else primarily because I know the anodization would likely eventually wear off giving it an uneven look . That said, I do have both a desert ironwood and g10 backspacer installed on two PM2s and a cf backspacer on my CRK Insingo. I like them.
Do they add more grip? Maybe they marginally do. My Insingo is the only one of the three with smooth ti scales. I would say the backspacer helps a little. The two PM2 have the anso style grip texture (both aftermarket scales) and it is harder to tell if the backspacers add any grip on those. Again, they probably do, but it is neither noticeable nor needed.
Weight? I do not really notice. YMMV.
They do not collect dirt in my experience. They are just an added little something to make yours different than the masses in a nice way that may add a slightly better grip.
As far as the cost goes, that's strictly personal preference. I like them, but I only have two on my PM2s and I have a few others with no backspacer on them and like them equally.
