It needs to be said, if you loved the previous Professor Layton games then you'll love this one. The presentation is better, the minigames are more engaging, more variety of puzzles, more voice acting and cut scenes, the quality of this game is faultless. It cannot quite compare to the emotional impact of "The Lost Future" but the story is unmitigated fan service, with nods the fans will love, including just how Layton and Luke met, and some surprising returns from old characters.
The only issue I have with this game is "London Life". For those of you who don't know, this was an extra minigame included in the Japan and US releases. It is an RPG which sees you living in London doing quests for characters of the games, and purports to have 100 hours of playtime. Many people are outraged that due to long localization times this game is not available in Europe (as although an english copy of the game is in circulation in the US, UK English, French, German, Spanish etc versions are not available). If this is an issue for you, I would strongly recommend importing this game from the US. If however you are not too bothered about this, I cannot recommend this release higher to you. The voice-acting is sublime as always (the UK voice actors are less irritating than their US counterparts), and this is the most complete Layton experience ever.
Even without London Life, this is a worthy package that deserves to be in your DS (or 3DS) for many months, fully deserving the same ratings that the other games in the series regularly get.