I went a few weeks ago. Practical things first:
Train timetables here:
http://www.b-rail.be/main/E//1. Trains from Bruxelles twice an hour, half of them direct. If you have to change, it's in place called Ottignies. Trains leave from Bruxelles-midi/Brussel-Zuid (southern station). However, I was a bit surprised to notice that instead of heading south and towards the museum, the train first takes a tour (that's an underground tour, so no sightseeing value there) around Bruxelles, stopping at least in Bruxelles centraal, Nord, Schuman and Luxembourg before actually heading south (those are from memory, couldn't find a list from the railway company site). Same applies to the return trip (and the station nearest to the museum is called Louvain-La-Neuve-Univ.)
Choose the one that suits you, unless you really prefer 15 stops in the metro, instead of sleeping half an hour more and walking two blocks into the nearest station...
Return ticket from Bruxelles area costs 9.60€, cheaper rates at weekends. Machines may not accept foreign credit/debit cards (didn't accept mine, had accepted the one from my friend a month earlier), but same price applies in the ticket office.
2. As said before, the walk from the train station is 5 or 10 minutes and signs start from the station.
3. Audio guide is very very good and free.
4. Museum shop offers the usual stuff, plus the museum catalogue. 40€ for a book the size of a phonebook. Brilliant work (or at least first 70 pages is brilliant, I forgot mine in the train between Bruxelles and Paris. Certainly worth the money if you keep it). Cheaper version is smaller than A5, maybe 50 pages and costs 10€, I recommend the expensive one.
5. There's absolutely nothing in the museum for kids (well, a park next to the museum). Fortunately I knew beforehand, and now you know - arrange your visit accordingly.
(Above took me few hours to find out, some web-surfing and some needless sitting on a metro/train. Maybe a good, short guide would be in order? Possibly too much to expect from the foundation, so maybe somewhere on this site?)
And then the substance part:
What I can I say? As you've possibly read between the lines, I'm not too fond of the foundation. I even admit going as far as thinking of not going. However, the museum is just brilliant work by them. Brilliant for a fan and brilliant for a casual observer. I must have visited hundreds (if not thousands) of museums in my life, and this one easily goes into top five. Easy for a quick glance where you think that's enough, easy to find more info. Always something around the corner that draws your attention, but you're not drowned into too much stuff to see. And enough space (=not too crowded, at least on a weekday) to take your time.
There are things that aren't touched (namely, nazi-accusations and personal life), but then again, why they should? The focus is on how Hergé worked, and that's shown brilliantly. From the moonraker model that was used at the studio, to the original strips that show the method, different phases of planning and corrections (that's something I'd recommend paying attention to, goes a long way in explaining why Tintin is what it is, a classic and a benchmark in comics. Second-last version usually looks very very
very good, but Hergé was aiming for perfection, and final version is exactly that.).
In short, a must-go for a fan. I'm tempted to write more, but that would spoil the experience a bit, wouldn't it?
One last thing, can anyone confirm or falsify the following? I think I read from somewhere that plates on sight are changed every four months? At the time I understood it meant the permanent exhibition, but it could easily mean only the temporary exhibition (currently Tintin and trains, until August). I hope it's the former, there's certainly enough plates to do that. Not planning to visit that often, but maybe again in few years time...