I invested some effort to keep it performant even with fairly large CSV files, including a custom port of some C++ code for fast CSV import. My current favorite example is the Met Museum's 228MB 450k row collection data set; takes about 12 sec. to open in Tad on my 2013 MacBook Pro. Definitely not lag free (and hard to achieve that without going to some serious column store data warehouse like Amazon Redshift), but still reasonable. https://twitter.com/antonycourtney/status/869252722624561152