They are great boats. Was fishing in a 17.5' this week and really liked it. The two aluminum boats that have impressed me are Alumacraft and Lund.
Not sure replacing rivets is easier than welding. It depends on how much stuff you have to remove to get to the rivets. Unless the manufacturer forgets a rivet, which does happen on some brands, it is usually more than one rivet that leaks. Welds can and do crack, so rivets, if done right, are a good choice. You will most likely have many years of enjoyment with it before you have any trouble, if ever.