Two DMs I know actually bought them when they first came out (One got a discount from the distributor because he worked there), and I have played with them in a few different ways. Here's my experience and stand on each, including alternatives I've seen/tried:
1.
Master Maze: Bring them out and play randomly, setting up on the fly - I agree with Pogre, that if you can have them near the table in shelves or anything other than the original boxes, it's not as quick and potentially not worth the trouble. Like anything, it takes getting used to. Back then, there were ALOT less variety in parts.... so we had to improvise for many things that are common pieces now.
2.
Master Maze: Pre-set up - This is a decent way to use them which lends itself to dungeon crawls or even tournament style games. One of the DMs I know used black felt/velvet to cover the entire dungeon, pulling back pieces as we explored. Especially handy is having more than one table to use... so you can go over to the dungeon table when you need to. I thought this was a neat way of doing it, but very time/space consuming. If you use your dining room or coffee table to play, then this would clearly not be good for you.
3.
Hirst Arts - This is something I would only advise you to get into if you love Legos.

If Legos were your thing, you will essentially be a kid in a candy shop with these. Bruce Hirst does quality mold work, the molds hold up well as long as you follow directions. The flexibility of design FAR outstrips the Master Maze items. I find making these kinds of things VERY relaxing, and I don't watch TV (not at all. Yes, I'm weird. I like TV, just don't watch it) so the times people would be watching TV, I'm probably doing this or painting minis. That's how I have the "extra time" to do it, so consider that if you're interested.
Additionally if you are serious about doing the molds, I recommend making some space you can set up as a permanent work area. The website also has a How-To for building a vibrating table (!) which helps making good casts in ANY mold ALOT(!!) easier.
4.
Cardboard/Cardstock miniatures - This is currently where I found a balance at. The best provider I've found so far for fantasy and present day type architecture is
World Works Games. They have expanded their lines and have a great message board that has tips on everything including the best tools, best practices, and even the best printers for 110lbs Card Stock. For those of you looking for Space (or like me, Star Wars) themed stuff, let me direct you to the following places:
http://www.swminiatures.com/ -
http://www.basecontact.com/. Though I've also used the First Light & Mars Station from World Works to great effect in my SW campaign.

It also helps that I was able to get a color laser printer for two hundred bucks that can handle the thicker card stock in the feed tray.

This is the fastest way to make scenery for any game that I've found so far that doesn't take forever and a day but still looks pretty good.
5.
The Space Between - A battle map with things drawn on them, then a model house (perhaps the kind that model railroads use) and some scale trees and bushes (Games Workshop type stuff, or from any craft store) can add just a splash of scenery and get the imagination flowing, but without all the cost/time/aggravation of anything else. Sometimes just that is better than nothing.
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All that being said about Master Maze, I also agree somewhat with Mouseferatu on the "can't see anything(!)" comment; you can't. I end up standing up during gaming a fair amount though (6'2" height, with most of that in my legs, so I'm either slouched or standing.

), so it's not a big deal for me as it is for him evidently. I think the immersiveness gained by using scenery with miniatures makes up for the not being able to see easily from a seated position.
The bottom line is that if you are going to use ANY scenery, line of sight from a chair at low angles is going to be a problem. Period. For my money, what the scenery adds to the game is greater than the (questionable?) inconvenience of standing. A combination of MM and Hirst or Card Stock may make the money part not as bad.
In the final analysis, I like making crafts... A lot. I'm crafty.

So molding with Hirst or Designing/cut-pasting/printing scenery is right up my alley and something that I really, really enjoy doing. I have a lot of practice at it now, and I was a computer-aided designer for a number of years professionally... there is no real "learning curve" for me anymore. Be forewarned though, especially with the Hirst Arts molds... The time needed to make any scenery if you are a perfectionist is HUGE! I can easily spend days on the scenery for something that took me an hour to prep as a DM, but I know for a fact that I am slower than a fair amount of people at it because of that anal-retentive attention to detail :\
Woo... that took a long time. I hope all that helps!