There are so many great things about this hotel that it's hard to know where to start. So here's a list...

The Good:
Fabulous views of the Tokyo skyline THE most comfy and enormous bed (we reckoned room for five, although we didn't test that theory!)
Great bathroom - shower, nice deep bath, double sinks, separate toilet complete with plenty of buttons (very Japanese) Great location near Shinagawa station which means you can get anywhere very easily (never took a taxi the whole time we were there) You can also use the facilities in the two adjoining hotels - Takanawa Prince and New Takanawa - including business rooms, breakfast, restaurants etc etc
Very friendly and helpful staff - nothing was too much trouble to sort
You get rewarded for being environmentally friendly - like big hotels these days, there's the usual request to reuse towels, which considering the number you're given is certainly no hardship. In return you get a voucher to spend in the hotel's shops/bars/restaurants - as I try to do that anyway, you get to feel virtuous and get rewarded. (Even if you opt for this, they change the linen on check-in/Check-out and every other day anyway, in case anyone is worried about cleanliness standards.)

The OK (certainly not bad though!)
Room service was good but not desperately cheap, but it's so easy to eat out it probably won't matter. Same goes for breakfast - fine but nothing to get wildly excited about (good coffee though)
The wine bar wasn't the most happening place - we checked partly for the novelty (made a change from sake and beer) - but as we were spending our vouchers (see above) it was a freebie anyway.

The bad:
Nothing. Honest. I genuinely can't think of anything I'd change. (Well, unless they could make it free - but compared to hotel prices in other big cities, like London, it's a bargain for what you get)

Thanks to numerous business trips to Japan over the last 5 years I have gotten a good sampling of hotels in the country. When my girlfriend and I decided to celebrate my 50th birthday in Tokyo, we naturally picked the Sakura Tower as it is the only one (including several in the Prince chain) that I can't say anything negative about. I always get a south facing king size western style room on the 10th, 12th or 14th floor and can't review any of the other room styles. These rooms are really big by Japanese standards and the bed could comfortably sleep a family of 5. Furniture is high quality matching solid maple. Bathroom has both a large tub and frameless glass enclosed shower. Toilet is the popular Toto with the usual array of electronic buttons on the seat. Everything is impeccably clean.

We find the location very convenient as the Shinagawa station across the street has Narita Express to the airport, Shinkansen to Nagoya / Kyoto and Yamanote line to the rest of Tokyo. Getting to the nightlife in Rapongi requires either a train change at Ebisu or a $15 cab ride.

The staff is very helpful. If there is no taxi outside the front door, the doorman will sprint down the drive to fetch one from the train station. My girlfriend was new to Japanese money and accidently got shortchanged when buying Yen at the front desk. They caught the error in their nightly audit and immediately sent a bellgirl up to our room with a note of apology and a request to come back to collect the rest of her money. If your Japanese is no better than mine, the the front desk is happy to phone for dinner reservations on your behalf or write street addresses in Kanji for the taxi drivers.