We traveled to Paris the last weekend of May 2010 with our 7-year-old son. We arrived during a train strike and chose to take an expensive taxi ride from CDG airport. After a horribly long and painfully expensive taxi ride (100 euros when you get caught in traffic!), the Adagio City Aparthotel Montrouge was like a calm oasis from the chaos of Paris.
The front desk was very pleasant and helpful - told us where to get groceries and when the stores closed as we arrived late. The best part was the view from the balcony. We were on the 6th floor and had a clear view of the Eiffel Tower, which made my son's trip to see the Eiffel Tower lit up his first night there!!
We found the room, kitchen and bathrooms to be clean and comfortable. Looked as if it had been remodeled fairly recently. The beds in Europe will always be hard for Americans, but these beds did not make my husband's back hurt, so that's a plus.
There is a small grocery store one block away and a huge grocery store two blocks away. Go one block the other direction, and there is a bakery. We used the kitchen to make breakfast, keep water and drinks cold (saves a LOT of money to buy from grocery stores and carry in backpacks) and store wine and snacks for the evenings!!
As for transportation to the metro, walk across the street and take Bus #126 four stops to Metro D'Orleans. The bus runs all hours - we took a late-night bike tour and got back to the metro stop at midnight - plenty of time to catch the last bus at 12:20 a.m. In fact, every time we got to the D'Orleans metro stop, there was a bus there waiting.
We bought a Paris Visite Pass at the airport, which covers bus, metro and train. Traveled everywhere on those passes, which made it worry free. All bus, metro and train schedules are clear and easy to use. My 7 year old mastered putting the ticket into the machine himself at the metro, and I can say that it was family friendly. Even coming back at midnight, we felt safe.
If you're coming from the airport, I do not recommend a direct taxi ride. Take the RER train or Orly Bus to the closest stop (probably Denfert Rochereau), and then take a taxi. You do not want to carry bags up and down the stairs in the metro stops!!
If you're looking to be close to everything and nightlife, then this is not the place for you. If you want more space than a hotel room, the convenience of a kitchen and a quiet, peaceful night's sleep, than I highly recommend the Adagio City Aparthotel Montrouge.

I stayed here for two nights with a large group (19) students and two other chaperones. The hotel was nice, the breakfast was very good, and the students liked the hotel a lot.

However: it is far from the metro (at least 15 minutes' walk, mostly uphill on the way from the station to the hotel). As well, it's at least four (probably more) metro stops from the center of Paris.
The staff did not seem that helpful, or really that bright.

It was ok, the rooms were nice and I appreciated the kitchenette in my room. The bathtub was lovely after two days of walking Paris. If you're only looking for a place to sleep, this will do the trick.

I was not impressed by the hotel: the rooms are small and not so clean (especially bathroom). The location is far from the city centre and also from the underground station (15 minutes walking).
It could be ok only if you look for a cheap solution and you are not interested in enjoing tha nightlife in Paris.

Stayed here with the family - did not pay a great deal (30% sale) and so did not expect much, but was still disappointed. Standard of service was mixed - one chap was very helpful whilst a lady was as indifferent a hotel member of staff as I have ever encountered. The room was not as clean as I would have liked - the carpet was very badly stained and the room had a strange odour. The residents of the room immediately below ours were noisy into the early hours of the morning and smoked incessantly on the balcony below ours (so we had to keep the windows and doors shut) which did not endear the hotel to me either. We stayed for two nights and did not want to stay longer probably ok as a one night stopover. The hotel is located approximately 3 miles from the main tourist attractions and is not in the most family friendly of areas. If you can afford to spend more, spend more and stay closer to the city centre.