Thumbs up for Diorissimo! Tried it last week for the first time myself - a very nice jasmine-muguet chypre.
You know, it's funny, you have so many of perfume's "star" flowers growing down there - jasmine, tuberose, gardenia - that I forget that it's probably far too warm for lily-of-the-valley. Diorissimo is more full and interesting than the real thing to my nose... lily of the valley in nature is a very "pure" fragrance, like a beam of white light, rather than complex flowers like tuberose, rose, jasmine etc. Even cheap fragrances tend to recreate it fairly well ( if make it a little overpowering, at times ).
I've heard the parfum strength is the better version of the modern stuff, but I haven't tried it myself.