Those interested in using the PS3 as a Blu-Ray player will likely be interested because there are always a lot of releases in other regions that don't appear in your own. Those into Japanese horror and Manga for example, and even limited edition versions of films in different regions. I don't know if the BD film releases are effected in the same was as DVD was, but with DVD releases often the same film could be of very different quality in different regions, with US releases often being a high bittrate and cleaner image. I for one would love the ability to run US and Jap discs in a UK PS3.

Regarding running PS2 games. It is really keeping things tidy. If the PS3 could run all PS1, PS2 and PS3 games then no other systems would need to be setup, and with it all going through an HDMI cable produce a better image for everything. An all in one solution.