MM is one hell of a game, but I wouldn't buy one now, even if I had the money. Had you asked me back in 1999 or earlier, yes definately.
The game is way too expensive for the bang, you can get, for the same buck. For one MM, you can get a handful of triple AAA games (even more, for B or C-list titles).
LOTR does play very similar to MM, and may be the appeal. Doesn't hurt that LOTR is way cheaper than MM.
MM is better thought out design-wise. LOTR's "Paths of the Dead" is universally acknowledged as flawed-design. Ultimately, it falls onto player preference, game-play wise. MM also looks considerably better than LOTR art-wise. I wish Stern would one day stop with the godamn Photoshop already, in order to save a buck.
Investment-wise opinion for MM is debatable, unless you got one last century for a bargain of a price, and were planning to sell yours eventually.
Pinball collection-wise, it isn't considered a good one, with the amount of good games you can get for the same money for 1 MM machine. Opinions with large wallets may vary.