If the sequel has more interesting environments, while still allowing good amounts statwhoring, I'm all for it.
I wasn't keeping track of the number of environments specifically, but there are three main overland areas in Act 1.
With exception to the first, which is a linear game introduction sort of thing (I'm sortof hoping they'll redesign this for the final game), each of these is a rather large area with a variety of regions (For example, the second one has a camp of trappers who, obviously, laid bear traps everywhere
which really hurt!)
Personally I hope they have more interactivity with the environments ala the fixed maps with puzzles in Torchlight 1.
I've seen
a puzzle. I'd say there's just a really really low chance for that chunk to spawn, and there's only that one chunk in the beta. With that in mind, there will probably be more puzzles in the final game.
There are a few interactive elements that weren't seen in T1 either -- a golden chest that requires a key from a particular mob to open (the loot from these is extremely crappy at the moment), a wall statue that requires a gemstone (a drop from a nearby Champion creature) that activates a teleporter to a small pile of loot (again, crappy stuff, but it's a nice concept), bandit camps with prisoners who will give you (absolutely AWFUL) loot (I REALLY hope they improve the loot table for these... not once did they give me anything even REMOTELY useful), ghost chests that are locked until you defeat the ghosts haunting them, etc.
In any case, mods are your friend if you find the game isn't up to snuff already.