No DVR's search functions can be guaranteed to be 100 percent accurate, of course, but the TiVo software comes closer than any other DVR. In fact, compared to the primitive functionality of most cable company rental boxes, TiVo laps the field. I have had 5 TiVos since 2000 and and am currently running two, a Series3, which has been in daily use for nearly 6 years, and a Premiere Elite, which I got early last month.
As other posters have pointed out, TiVo's Wishlist function is a powerful tool. There is a reason why so many of us who are longtime TiVo owners are fanboys.
HT setup: Sony 75XBR X940D UHD HDR TV; Kaleidescape Strato Movie Server 6 TB; Yamaha RX-A3060 AV receiver; Crestron Control System; Hsu VTF-3 MK3 Turbo subwoofer, 6 Hsu HB-1 Bookshelf speakers, 1 Hsu HC-1 Center speaker, 4 Focal ICW8 in-ceiling Atmos speakers; Oppo BDP-103 BD player; Mac Mini HTPC. TiVO Bolt 1TB DVR; TiVo Premiere Elite 2 TB DVR