I've never had a TIVO but I can tell you the following after using the Tablo 4 Tuner for 3 years now.
- 2TB WD Elements USB will work fine
- Support for Tablo is fantastic and they answer in a timely manner
- Their software is constantly improving. When I look back just 3 years OMG what a difference!
- If you get a Tablo go all in and buy the lifetime guide instead of monthly or annually its worth it.
Last but not least, don't go cheap on the TV antenna. Most of the problems people have with the picture breaking up etc... is not the problem of the TABLO/TIVO it is the antenna. Go out and buy yourself a good in door or out door antenna (prefer outdoor as they are the best).
I wen't nuts with mine (all tool time) and purchased two massive antennas
I bought two of these 8 Element Bowtie Antenna
Those are only UHF antennas, so I then had them connect into a VHF antenna so I bought one VHF for each of those VHF Atenna
I then had both of them go into two pre-amps. Reason two is you want them as close to the antenna as possible so I have each of the mounted just below the black box you see in the picture of the 8 Elements Bowtie. Pre-Amp Channel Master CM-7777
I then combined the signals from the two antennas about 10 feet from each antennas using this DC/IR passthrough combiner. This needs to be a DC passthrough for both routes so the power can reach the pre-amps (yes one pre-amp power supply can provide enough power for both amps) Channel Plus DC/IR Splitter/Combiner
Finally just get any coaxial cable that is Quad Shielded, do not forget to ground that wire before it enters your house if not you may get a surprised FRYING from a lightning bolt.
With that setup (which I went completely overboard) was to help me point one of those antennas to DC and the other toward Baltimore. I get over 80 channels and 99% come in crystal clear with no problems. The last 1% are because they are comming out of Pennsylvania so it just depends on the time of day because the distance is huge (200+ miles away).
Point is, don't go cheap on the antenna. Go all in, I did and it cost me allot of upfront costs but I do not regret it.
EDITED: I forgot to add one really important thing
The coaxial line from the antenna to the Combiner from each antenna must be the exact same distance. If not you could get ghosting on the TV because one antenna is behind than the other.
EDITED: Added some pics as request (it was foggy and I took them this morning)