Sharp step up for Wii Sports fans, but worth investing the time to get moving up the ranks.
Graphics
They've gone for the 'sims' look, which works really well in the game. The GAME assistant kinda pitched this as a negative but I've found it to be helpful in softening the hard learning curve. Having just been to Wimbledon I can vouch for the accuracy of the courts and this helped create an engaging atmosphere.
Sound
Sound effects are great - feels like I'm on the grass/clay/gravel. Music is well matched for but feels a bit limited. Commentary could do with a bit more attention, which lost this game points for me - a very limited stack of phrases from Pat Cash gets boring pretty quickly!
Difficulty
Even on the easy setting you'll trip quite a lot at the start while you get used to how the controls respond. DON'T PANIC! Invest a few hours into it and you get your mojo.
The practice court seems fairly straight-forward but it doesn't prepare you very well for the actual games, so my score has been lower because of this.
Motionplus
Guy in GAME said this game was unplayable without the Motionplus but I disagree, I've been playing against friends no problem without it (even when they have). At the very beginning you won't notice much difference other than the weight in your hand.
However, I have started to notice some techniques are harder to pull off without it fitted and I guess as you get further into the game you'll need the extra avenues to improve your play.
So I recommend getting one! (or using it, if you got a bundled copy of the game)
Life
Plenty. I have no benchmark for comparison but there is a clear number of ways you can 'gradually' make the game harder to increase it's lifespan. Aside from the usual easy/normal/hard settings you have full control over how many games per set and sets per match are required to win. I've started off with a quick 3 games needed while I get the 'swing' of things but fully intend on increasing this as I learn new skills.
You've also got lots of legend abilities to win in some of the games, which will increase your foot speed, or accuracy, or particular styles of play etc.
Summary
I'm loving Grand Slam Tennis so far and can't see me getting bored of it anytime soon. I'm excited to see how finely-controlled you can get with the Montionplus and this will definitely keep me going until Sports Resort is released in a few weeks time :)
Peace Out
Pobus