Cliffs:
You'd have to already have a desktop PC and be comfortable with adding expansion cards and installing drivers, but I've had good luck with a Ceton InfiniTV 4 (Newer model:
Ceton InfiniTV 6 PCIe - PCI Express CableCARD Tuner). You can get the newer InfiniTV 6 for $300 or the 4 on Amazon for around $185. I want to say I paid ~$240 back in 2012 for mine. It quickly paid for itself vs renting an inferior DVR from the cable company though as Comcast charged $18 a month to rent a POS DVR and it only got a LOT worse from there if you wanted a "whole home DVR" (you can hook as many used xBoxs up to that Ceton card as you desire, no monthly fee).
Long Winded Review:
I got this card almost 2 months ago, and honestly the only complaint I have so far is with Windows Media Center, and it's a minor one. We have Comcast cable & Internet, and the Comcast DVR was always a source of annoyance. It only had 2 tuners (a real hassle when 2 shows were recording and a game was on), its hard drive was constantly filling up, and with the monthly fee + tax on that fee it was costing us $19 a month.
So I started looking at computer TV tuner cards to replace the DVR. Originally I thought I'd have to hide the old desktop behind the living room TV stand to do this until I found this card. What I ended up doing was leaving the desktop in the storage room and hooking an old xBox we bought used up to the TV. Our router was already next to the TV so hooking up the xBox was no issue. I did have to get a 2.4 GHz/5 GHz dual band router in order to stream HDTV to the xBox without issues since the desktop is using wireless. I really needed to get a new router anyway, with this new router the wife and I can download stuff from the Internet while streaming HDTV to the xBox ... and nothing lags
Ceton sales an extender for $180 to hook up to your other TVs, but you can get used xBoxs on Amazon for $120 or so. We got a X-Link remote for the xBox on Amazon for $21 and the wife and I are very happy with our xBox as a cable box/DVR setup. We already had the xBox so our only setup costs were $200 for the Ceton card + $21 for the xBox remote, but I realize not everyone already has a xBox.
Installing the Ceton card, installing the drivers, and setting up Windows Media Center was very straightforward. Ceton includes a step by step instruction guide in the box. Comcast was nothing but helpful in getting the cable card, which is free. Maybe they're losing too many customers to the Genie and Hopper? Once you install everything you call Comcast, they activate your cable card, and you're up and running.
It's a good idea to download & install Remote Potato once you're up and running. Remote Potato is free software that allows you to access Windows Media Center remotely from other computers, iPhones, Droids, etc. You can access your TV guide, schedule recordings, even watch recordings via Remote Potato.
My only complaint is that Microsoft doesn't allow other computers to act as Windows Media Center extenders like an xBox does. This is not a complaint with the Ceton card, just something that Microsoft should have included in WMC long ago. It's kinda dumb they don't allow you to simply use WMC on other computers as a 'dumb terminal' back to your desktop HTPC.
I looked at DirectTV's Genie and Dish's Hopper and the problem is they require a monthly fee for the main DVR plus a smaller monthly fee for each 'slave DVR'. Comcast has a Anyroom DVR, but it only allows you to watch recordings on the 'slave DVRs' and has a hefty monthly fee. With Ceton's card you get a free cable card from Comcast and that's it. No monthly fee. With the $19 a month we were paying for a Comcast DVR this card is paying for itself in less than a year, and does a LOT more than that DVR did.
Pros:
Storage is only limited by your computer's hard drive, and HDs are cheap
Whole home DVR with no monthly fees, the only option for this I'm aware of
4 tuners
hitting the Eject button on the xBox remote causes our cats to jump, useful for when they're getting in front of the TV
Cons:
You may have to buy a new router if your computer is wirelessly connected in order to stream HDTV without issues
Be careful running Windows Update, I had to run TV setup again in Windows Media Center after one update and restart twice to get live TV working again