VM is made from many Cable companies and the last big take over was when NTL & Telewest joined to become VM ( which at the time a rented name ).
Telewest was first to start a Digital service with HD TV recording TV box and as both networks were so different that it took years to get both networks to work together under one .
So we have a cable network that did 0 to update it self until TiVo came along and changes to cable software that change the way services were delivered our homes.
YES TiVo has become a lot slower as we see other Items like our TV's which have become Internet ready and can record if you put a USB stick or Hard Drive to them. We have also seen other companies box from the like of freeview, freesat, BT Sky Talk Talk PlusNet NowTV and other have faster quicker newer software & hardware. Also items like 3D Blu-Ray player with internet and quick playing etc.
TiVo has had few mini updates and now Three big updates from day one and the last give us many extras but doing that made it having to work much harder then ever and TiVo boxes being made by different factories can not help too.
TiVo network was only 2Mbps at the start now it has take SD, HD players and load images to shows etc.
Internet speeds have gone up very quickly to now 200Mbs & now for some 300Mbs..
Numbers of TV channels have grown faster in the last few years with SD and more HD giving a large choice on top a number TV players.