I don't see how anyone can watch the first three movies and then never watch a single episode of TSCC? TSCC is a great 'series', if you're going to watch don't expect 'shoot'em up, slam them down' action in every episode! that's not what you get with a series.
If you want 'come with me if you wanna live', blow **** up. The End. then stick with the films.
You get more characterization and backround stories in the series, (which is why American audiences didn't like it, they can't watch anything that requires an ounce of brainpower) and yes Summer Glau is amazing as Cameron, the female infiltrator turned protector. Then again, Glau is pretty much amazing whatever her role. Check her out as River Tam in Firefly and Serenity where she plays a 'broken' mind reading genius. Then check your Hollywood DVD collection and name another actress who could have done a better job!
So yes, Summer Glau for Terminator 5, and through in another series of TSCC while your at it.