The problem is bad even for small files; the key example being project-wide searches in things like Rails projects (very small files, but lots of them; all of them are kept in memory).

Vim, Emacs, any serious editor — even BBEdit, Xcode et al — handle these workloads easily, and that’s exactly what one would expect. The technology for handling this sensibly has existed for decades.

TextMate’s failure here is very disappointing, and the glacial pace of development of the new version doesn’t offer much hope (nor are there any guarantees that these bad design choices aren’t being carried forward into the new version).