I love this game, but I can see how many wouldn't enjoy it.
If you are looking for something with instant gratification then this is not your game. If you're expecting Dynasty or Samurai Warriors then you will be greatly disappointed. The Challenges are the quickest things and they still take half an hour minimum. The Local Mode games take 10 to 15 hours and the Unification Mode games take 40 hours on the short side. The game doesn't track your playing time for you directly so it's really hard to say.
The game shines in my opinion because it has two modes that flow together well: planning and active modes. Planning mode is where you issue orders and is similar to most turn-based games; at first this is what I was most comfortable with. The active mode is when orders are carried out; this gives the game a real-time strategy game feel.
This game is quite different from the last Nobunaga installment. The battles happen in the open for all to see so you can gauge your opponents when they fight each other. Coalitions spice up your game even when you're the big fish. It doesn't have a "Kessen" mode so it the end game can get somewhat routine. Unlike every other Koei strategy games I've ever played this one has pooled resources so you won't need to ship rice and gold from city to city.
I am a huge fan of the Nobunaga's Ambition series. This newest installment is somewhat of a let down. While there are some interesting additions, there is also a major change in the over-all strategy of this game.
I suggest starting off in the second game play style, i believe it is called "local challenge". It keeps the amount of territories to a small area, which makes it a little easier when first getting your feet wet.
It can make a difference which lord you choose to play as, so take a look at their stats, and what the land looks like around them... The bigger the lord's land is not always the best thing. Each person has a different type of technology they excel in, which can make a big difference in winning or losing battles.
The battles were the biggest disappointment to me. They are in real time, now, which makes them much more difficult to implement any type of strategy to ensure a successful attack. just be sure to keep your technologies as high as you can, which means building a lot of academies... which can be difficult because if you don't have enough farms and shops built then you won't be able to fund an attack...
I suggest playing a small game, and not expecting to win it, but using it as a learning guide. examine the other lords, and how their area's are set up, which will give you a good understanding how to set yours up for the next game.
unless you like really slow paced, very strategic types of games, this may not be the one for you... but hey since you're just renting it, why not give it a go!