First, I'll mention the price. At the time of writing, this is 35 pounds in the high street and 25 pounds here - definitely worth the few days waiting for delivery.
I've played up to chapter 3 and so far, the description of 4-5 hours per chapter is complete exaggeration. I've been trying to explore everything, even out of the way optional places and I'd still put it as 2-3 hours per chapter.
The voices are all in English - unfortunately only the English PS2 version only available in the US also has the Japanese voices. The voices vary between really good and bad (often due to exaggerated accents) but not terrible. The music is great throughout though.
One note to make is the controls. They're confusing at times, but usually fine. It often throws you in with no explanation, but after the first chapter you should understand them. There are some awkward parts though, like not obviously marking a certain area where you need to go to get to the next area or not mentioning how to land on something. The exploration parts are fine though.
The storyline is quite cheesy overall, but there have been some good character-centric storylines so far.
If you like Sakura Wars in general, you'll probably love it (if only for the chance to see Sakura again, if briefly). If you like anime, you should give it a try and you'll likely like it. If you're not much of an anime fan, maybe rent it first. I do find myself wishing they translated the first Sakura Wars instead though.