Using SDV Adapters
Cable companies use two main SDV adapters in their systems. The Cisco STA1520 and the Motorola MTR700. It's hard to talk about features with devices like these since number one, you don't have a choice in which device your cable provider uses and number two, the only feature is the number of tuners that each one supports. If you're lucky enough to have a provider that uses Motorola adapters, you'll have no problem running a TiVo, Moxi (3 tuners) or a Ceton InfiniTV4 (4 tuners) with the proper firmware. The Motorola MTR700 can handle up to six CableCARD tuners and is ready to be used with any CableCARD device currently on the market.
The Cisco STA1520 on the other hand can only handle two tuners. The company has promised a firmware update but a date has yet to be set. For TiVo owners, this isn't a problem. If you're a Moxi or Ceton user however, you'll require multiple STA1520s in order to utilize every tuner you've been provided.
With Ceton InfiniTV4s, the only thing you'll need is enough open USB ports on your Home Theater PC. With Moxi units, which only come with one USB port, it is possible to use a USB hub in order to be able to connect two Cisco units. If you have a different DVR with only one USB port, you'll need to check with the manufacture to ensure that splitting the signal will work for you.
At this point I've only had the opportunity to use the Cisco TA (Tuning Adapter). So far I can say that I have yet to have an issue with them. They power up, are able to find the signal they need and simply sit and do their job. I've heard similar things about the Motorola MTR700 as well though I don't have an direct experience.
Again, since you don't have a choice in which tuning adapter your cable company uses, you're a bit stuck when it comes to using SDV adapters. Communication issues can definitely arise with these devices and should you have problems, your best bet is to call your cable provider and have a technician visit your home in order to fix the issue. This may require them to swap out your TA but once it's up and running you should be all set.