Yes, I've been a few times and is it worth it, well, It depends.....
It depends on what you want, as other have wrote it could been seen as a large department store of various household stuff. It also has a fair bit of cultural "stands" and it is on that theme, for me anyway, whether it is worth going or not. In past years there have been some great (and classic) stuff going on. Of these, 3 stand out for me:
1) the year the Swiss army turned up to show of their stuff - they even brought a helicopter and F-18 jet with them! - really cool to see up close.
2) The year SF built a full TV studio and broadcast many of their normal news programs from Basel instead of ZH. The whole studio was built so one could see inside and out everything that was going on during a broadcast - maybe a bit boring for some, but truely great for the inter geek in me

3) the year they invited (what seemed like) every model/hobby club in the Basel area. The whole of Hall 3 full of scale models of cars/train/boats/nearly anything else that could be modeled most of which where being run at some point or another....
This year nothing big on that scale, but the local tram company (BVB) are advertising that they will have a large stand to show us the future of transport in Basel (but bring indoors one of the old-timer "bar" trams

)
Every year they have cultural "exchange" with another country (Thailand for example mentioned above) - This year is India (IIRC), but strangley didn't invite any of the local Indian resturents to take part food wise, instead giving that "honor" to some place from Genf
Also, NEVER pay the full price to get in - it really is not worth it, As pointed out above, places like Ikea offer discount tickets - which, if I go this year, is were I'll be getting mine.
Based on the offerings this year, I'd say Muba this year was not really worth it, but that's just my opinion. It is great to look around for a rainy afternoon if there is nothing else planned, but not sure if it is worth a long trip for.
Hope that helps
Pat