I've skimmed through the reviews and scoured the personal comments, and carefully organized some key quotations to bring you the important things you need to know and what other people think about Hare & Tortoise. Perhaps you could call this a kind of "consensus of opinion" - biased of course, because I'm the one who gets to pick the quotes to include. Nevertheless, here you have it, an at-a-glance overview of some of the majority opinions that you need to know about this game.

1. Hare and Tortoise is an award winning classic race game.
"Hare and Tortoise is one of the first Spiel des Jahres winning games, and is justifiably called a classic."
"Hare and Tortoise helps math skills, planning skills, and is fun for both kids and adults."
"Classic strategic race game. One of the best ever."
"This is the best racing game ever and one of the best hand management games ever. Use your carrots and your turns wisely; plod along like the tortoise or take your chances with the die roll on the hare spaces."
"Unique strategy racing game. Sort of an advanced Cartagena."
"This is a BRILLIANT, fun game! I like the handicaps that are built into the system when players fall behind."
"Very original movement mechanic and plenty of stressful decisions for a game that can be explained in 3 minutes. A great way to introduce non-gamers and younger gamers to German board games and as the first SDJ winner, a worthy addition to any collection."
"An excellent race game that has less analysis paralysis, more strategy, and more interaction than first impressions would indicate. It strikes the right balance between tactical choices and mathematical calculations."
"This classic race game still gets played at our club and still packs a lot into an older design. Well deserving of Game of the Year and an entry in the Games Hall of Fame."

2. The fable-like theme and the visual artwork is appealing.
"The game is very attractive: a delightfully illustrated board, pretty cards and wooden tokens."
"Beautiful artwork."

3. Despite appearances, this is not a family game for young children.
"I believed I was getting a family game and Hare & Tortoise is NOT a family game"
"I'll play it from time to time, but I don't think I could talk my family into it."
"I would not recommend this for the lower grades. Crossing the finish line can be pretty difficult."
"Very cool game - looks like a kid's game but definitely deep strategy."
"I thought this might have been a kids' game, but it can be challenging even for a 10 year old."
"Note that despite the graphics that appeal to kids, because of the calculation involved, this game would be difficult for them to win without help. "
"Don't let the childish appearance fool you. This is a pretty deep game."
"Looks and feels like a children's game, but too difficult to be that."
"A 'kid game' on the surface, but has a lot of depth."

4. The amount of players changes the game, and it is perhaps best with four players.
"Although it says it's for 2-6 players, I think it plays best with at least four."
"I can't help it, but I love this game; particularly with 4+ players. "
"I do love this game, but tend to get it out when there are exactly 5 to play. Any less and the positioning is a bit too predictable, any more and the queues for the lettuce spaces bog it down a bit too much for my liking."
"I have tried this game with more than 3 and I did not care for how the game played. I prefer to play with three players."
"It plays well with any number, though it gets a bit chaotic with the full complement of players, and the length is just right."

5. There's a lot of math and tactical calculating.

Either you'll hate this.
"Like doing maths problems for fun. Without the fun."
"It's got a - very lightly - pasted on theme of a hare & tortoise race (although you are supposedly playing as both), but it really is just an exercise in number crunching."
"More of a pondering math exercise than a game."
"As a kids game, I think this is a tad too complex/mathy to be especially 'fun'."
"Too much addition and subtraction for my taste."
"This game is pretty interesting but there is too much math in it for me. I prefer the simpler and more elegant version of the mechanics with Cartegena."
"Ugly and tedious. Feels like a mathematics educational tool for elementary schools."

Or you'll love this.
"It's a very clever exercise in arithmetic which David Parlett has fashioned into an entertaining and unique perennial favorite.""
"Often people who've played it know that it's too mathematical and don't want to play again. However that's what excites me about it."
"Some people may like this type of game quite a bit with tactical interaction and denying people bonuses but it is a calculation game."
"It's held up well, has been published by at least three publishers over the years, and is still an excellent choice when you have 4-6 players and want an interesting race game that is more skill than luck."
"In theory, this is a brilliant game. In practice, it's pretty good. You are racing forward (and sometimes backward), trying to manage your carrots and simultaneously hurt your opponents by landing on a key square, or arranging it so that they start their turn on a numbered square that they don't match (or do, if they are overburdened with carrots near the end of the race). It's a great game for mixed (kids and adults) company because it teaches math, has a good strategy to luck ratio, and is fun."
"The Hare spaces are the hardest to discuss. Results can be wonderful or disastrous. Most people save them for when they're desperate, but others play them just because they like chaos. Take your choice."
"There is good variety in the strategies available and scope for tactical play too."

6. The bottom line: what you need to know.
This classic race game has stood the test of time, and whether you'll enjoy it depends on the amount of players and your taste for gameplay with tactical calculation.

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The complete list of Ender's "What you need to know and what people think about..." reviews:
http://www.boardgamegeek.com/geeklist/37595