It takes a little longer simply because the TiVo has to start recording the program before it can start streaming. It still only requires one tap to start the process, but because it has to start recording every time you want to watch something, it's not great for channel surfing. Plus, you could potentially end up with a bunch of little recordings to go back and delete.
However, if you frequently find yourself wanting to watch a second screen while the main one is otherwise occupied, it's a nice feature to have.
Download shows to go
Being able to transfer programs off a TiVo isn't new; the company's $24.95 Desktop Plus software for Windows has long allowed you to do that and more. (Roxio Toast Titanium software is its Mac counterpart.) The process is arduous, though, requiring the program to be transferred to a computer first, converted to a format that'll play on your device, and then sideloaded onto the device. The first two can be automated if it's a series you're recording, but otherwise it's not terribly convenient.
The Stream basically takes this down to two steps: select a show and tap "Download." Everything is done wirelessly on the fly, so there are no cables or computers involved at all. The app gives you a choice of quality and lets you know the approximate time it will take to complete, but once it starts, you need do nothing but wait.
Once a download starts you can view its progress under the My Shows tab, which is now split into two sections, On DVR and On iPad (or whatever device you're on). If you're downloading multiple shows you can edit the queue to prioritize the list. TiVo says a half-hour show takes less than 8 minutes, while an hour-long show takes about 15 minutes. In my tests it took about 5 minutes longer than those times, but this is going to vary with network speeds and whatever else the TiVo is trying to do, such as stream to other devices.
In all, it's a great experience, but it seems like it should do more. For example, you can't set it up to automatically download when a new show in a series is recorded. You also can't set it to download an entire folder of shows, such as a series you've recorded but haven't watched; you need to individually select each episode to download.
Also, downloading and converting understandably requires a lot power, and you have to stay in the TiVo app while it's doing its thing or else the download gets paused. You'll probably want to keep your device plugged in if you're doing a lot of transfers.
Lastly, as is the case with the desktop software, you can only download Copy Freely content to your device. For the most part that means no premium-channel recordings such as shows from HBO or Showtime.
The TiVo Stream isn't a necessity -- especially at $130 -- but it's a very cool addition if you've already got an iOS device. (Needless to say, if you're an Android user, you should probably wait till the app support is available before buying.) The wireless downloading is certainly nice, but the ability to have a mobile second screen comes in handy more than you might think.