I downloaded and installed poker770 just so I can test this (and because I like to bash on ipoker ♦) and this is what I concluded:
The client automatically downloads all kind of casino games in the background, and there's 33 (!) different slot games which adds up to a total of 495 MB's of data and that's just slots (videopoker, roulette, blackjack not included).
In total, the client takes up 715 MB's in 5702 files and until that data is not downloaded, it'll obviously jam your bandwidth.
Good thing they updated their FAQ.....
Spoiler
• What is the minimum system requirements to install the Poker770 software?
- Windows 98, ME, 2000, XP, Vista or 7.
- Pentium 400MHz or faster. CPU with at least 128MB of RAM.
- Minimum screen resolution 800 by 600 pixels with 16-bit ("High Colour").
- At least 30MB of free disk space.
There is a possibility that with every update more and more files are being downloaded or even redownloaded thanks to ipoker's professionality and cutting edge technology... ♦
In that case you might want to try and limit the download speed of the client with for example NetLimiter.