Il Boom is a very attractive B&B and the rooms are gorgeous. I cant be more positive than that as it didnt really feel very private, our bathroom was across the hall and the communal areas dont really feel as if they are welcoming, ie like you are intruding in someones home.
The breakfast provided was not great, help yourself to cereal, toast etc, we felt a more hearty breakfast was needed for all the touring but we are aware this is the continental style.
Trastevere is lovely but just a little too out of the way after intense touring of all the sites and a climb up a steep hill at the end of the day is not welcome! However, there are 2 buses which stop outside so if you can figure out the connections etc this would not be so much of an issue.
We would reccomend this B&B but with the en-suite room and with the knowledge that you are a little trek away from the main sites. We had a shorter / intense stay so maybe if you had a little longer and didnt feel so rushed this wouldnt be such an issue.
The owner is a helpful chap and is open to questions etc.

We agree with most of the positive comments about Il Boom; the decor, the beautiful terraces, views, friendly atmosphere, convenient and pleasant location etc. And it was very interesting to feel that we were staying in an ordinary apartment like the locals — "when in Rome..."

However, there were a number of things that slightly took the shine off the experience:

Having to pay in cash for a 4-night stay, which meant toting large wads of banknotes through the streets (whilst Il Boom is reasonably-priced by Roman standards at 155 euros per night for three people, that is the equivalent of a 5-star hotel in other capitals, say, Prague or Bangkok).

The bathroom of our room (Vitti), though very smart, had a lot wrong with it:
It had the weirdest and most uncomfortable toilet (see photos), which was ridiculously high and narrow. A smallish person was unable to sit with feet on the floor!
There was an impressive shower with an overhead rose and six spray nozzles down the sides, but none of the latter worked and the overhead one could not be adjusted.
The shaving/makeup mirror was mounted so high that I had to tilt it downwards (I am 6' tall), and my 5'3" wife found it almost impossible.
Oh, and there was never any hot water in the late evening (from about 11.30pm), so a wash or shower at bedtime was not possible.

Some of the facilities advertised on the website were not quite as described:
"Quiet" is not accurate for a building located on a main through road and busy bus route (although that is obviously the price you pay for convenience).
The computer provided for guests' internet access did not work. "Sometimes it works and sometimes it doesn't; mostly not, I think. Maybe I should throw it away and buy a new one".
The DVD library, whilst extensive, is entirely in Italian — perhaps a note to that effect on the website would be helpful (and of course, all the satellite TV channels were Italian only).

Saving the worst criticism for last: in a 4-night stay our bedroom and bathroom were never serviced or cleaned at all, nor the waste-bins emptied. It does state on the website that this is done every three days, which is pretty poor at these prices (see above), but NEVER? That is unacceptable.

We did enjoy our stay, and it was an interesting experience, but I am nor sure if we could recommend it.

Il Boom was our first stop on our Italian honeymoon and we could not have chosen a better place to begin. Where to start? The neighborhood is gorgeous and feels light years away from the bustle of central Rome (and the hordes of tourists), even though you can walk to the sights in about 10-15 minutes (or take the tram). We didn't use the metro once and were able to walk to everything we wanted to see easily (what's a half hour walk to the Vatican when you are passing by Bernini statues and ancient Roman architecture all the way there!). The Trastevere neighborhood itself has so much to offer in terms of restaurants and bars and the church in the main plaza is lovely. We spent our first day just wandering the streets having a great time getting lost.

The B & B owner, Angelo, is very nice and the rooms are very well-decorated and comfortable (we stayed in the Loren room). After our subsequent stops in other parts of Italy where two twin beds pushed together seemed to be considered a "matrimoniale", we really could appreciate how big and comfortable the beds at Il Boom were.

I will say that in general we found that in Italy there is less of a focus on "customer service" than in the U.S. - staying in B & Bs is more like being a house guest and less like being hotel guest - so there is not someone always around to answer questions or wait on you - but that was just fine by us (if we wanted that kind of treatment, we would have gone to a fancy hotel). What we got in exchange was a real sense of a place and a feeling when we got back every day from sightseeing that we were coming to our own home in Rome.

We stayed here for three nights on our first trip to Rome. The neighborhood is beautiful and away from the bustle of downtown Rome. It is still close enought to walk everwhere, though. The owner (Angelo) was extrememly sweet and helpful. The rooms are all beautifully decorated, and they have three very friendly cats plus turtles who live on the roofdeck. We stayed in the Monica Vitti room. The bathroom was just outside our door and was spacious and clean. There is free internet and a bus that stops right outside the B&B that takes you downtown. Angelo speaks perfect English but was also very willing to indulge my terrible Italian, so I could practice. We would definitely stay here again!