More Multiplayer Appeal then Single Player Appeal, but much like Mario Kart found endless ways to keep me entertained.
The biggest knock for me in regards to this title was the fact that it did not support the Saturn Multitap, and limited multiplayer action to two players which considering that Mario Kart 64 supported four players was somewhat of a drag but did offer me a different experience, I found that I was often shuffling between the N64 and the Saturn when friends were over because Sonic R did have some appeal to it that kept drawing us back to it.
The SIngle Player Mode is short, you should be able to polish off the tracks on normal with one character in about an hour, and even if you really expand it and play with every character the experience at best will give you perhaps ten hours? and generally you have done everything that single player has to offer.
The controls for Sonic R are very much like any "Kart" style game and are easy to pick up, there is not all that much different about the game then your standard Kart game except for the characters, which leads me to believe that if you got a lot of player out of the SNES or N64 versions of Mario Kart you will find a way to enjoy this title, but if not Sonic R offers you nothing that is really unique that will sell a gamer on the genre.
Graphically, this is the first time that Sonic made the leap to 3D and you have to expect some hicups along the way and there certainly where some, but overall the game offers you a rich and colorful experience that rival anything else in the Kart genre at the time, the characters all looked good and overall I have nothing to complain about other then the few glitches which are few and far in between, the odd break of images here and there which correct themselves after a second are something I could point to if I wanted to be really nitpicky,
The one aspect of the game that was simply unique was the soundtrack, more often then not we get a standard midi style soundtrack which is unique but overall very forgetable, Sonic R actually offers a soundtrack rather then a midi score the soundtrack actually had vocals which really aided the overall presentation of the game. The effects were excellent and will be appreciated by any fan of the Sonic series, for the time this set the benchmark in this area.
From a replay stance, it really depends.
If you are looking for a deep and drawn in single player type of racing game this is not what you are looking for, if you want to mix up the usual mix of games you play when you have friends over, the I would very much suggest this title.
Overall, its a game that for its time got a lot of play perhaps the most of any Saturn Game (outside of theme park) and it was always a solid experience, I have recently started playing it again and it still is a lot of fun, worth a look for any Saturn Owner.