There isn’t much between one and two lines. One line is 16 pixels, so two will be around 32 pixels and the icon is presently 32 × 32, which is a good choice since it’s one of the sizes that icons are normally drawn at (i.e. no bitmap scaling, although presently some of TextMate’s own icons need to be redone in the larger resolution). 

So if anything, we should go back to a single line: Reading the items with a single line does seem easier.

Yeah, i agree. It wasn't really a complaint as such though, for me personally I usually type enough so the item I want is first or second, so Im not having to scroll down the list much anyway

One big improvement of the new dialog whether its single line or double, is that it shows the paths immediately (maybe this is related to the ranking you mention). 
Previously it filled the list items first, and then went back to fill the paths in which caused a delay if you're working over a share

One thing I've noticed is the list selection resets sometimes while the
list is filling..

This will be fixed in next build.

Excellent, thanks!