Wow! I picked this up as a spur-of-the-moment purchase along with something else, not expecting anything, but was completely hooked. I took it along on a two-day walking trip where myself and three adult friends found ourselves rained in for one whole day. We started playing this about 2pm and were still going strong at 8pm when we stopped for dinner. After dinner we played again.
The concept is simple and not dissimilar to gin rummy, although played with counters (that look like Scrabble pieces but with numbers) instead of cards. The aim is to get rid of all your counters by switching around patterns on the table. The added catch is the one-minute time limit, which cranks up the tension and excitement.
Putting it into words doesn't do it justice. It had myself and three other intelligent adults from a range of cultures (the UK, France, Hong Kong and Australia) completely hooked. We laughed, shouted and grew increasingly excited, and as soon as we got on the train to travel home, we whipped the game out and started all over again.
I can't speak for its durability, as I have had the game only a short time, but I can say that for a travel game it is fantastic value for money: it great fun, light and takes up almost no room (especially if you ditch the racks, which you don't really need provided you can hide your counters from opponents).
I would add just one small gripe and one warning. The gripe is that the instructions are clearly a poor translation from another language, making them pretty tricky to understand at first. I think it took us close to 45 minutes to get started. The warning is that Rummikub is a sloooow game to begin with, so you have to stick with it. I promise it gets better, not only as the game progresses but also the more you play, as you start mapping out strategies.
Thoroughly recommended.