Consider TiVo Premiere
to be the standard by which all other DVRs are judged.
I've been having good success with digital tuner cards and Windows Media Center under Windows 7 and under Windows Vista. If you've already got a PC, it lets you turn it into a very capable DVR for less than $100.
i7-4770K, H70, Gryphon Z87, 16 GiB, 980Ti, SSD, 2 HD, Blu-ray, SB ZX, TJ08-E, SS-660XP², 3007WFP+2001FP, RK-9000BR, MX518