In the past, I've recommended/suggested Bpartner to many users of this board - including yourselves Mack (Sun Palace) and bpi (Mor utca).
I've met with Dezso/Bpartner/Hungary a couple of times, as well as almost all other major management companies in Budapest over the few years I’ve been here.
In general, property management is very underdeveloped in this city and probably one of the weakest areas in the Bp property industry. Most companies seem to make their biggest profits from furnishing apartments, rather than renting them. However, most have little real design experience and do a very poor job of this. In addition, most generally charge significantly more than the furniture costs. The second major problem is that most people who live here don't know of the existence of several of these companies. ingatlan.com is the closest Budapest has to a daft.ie, but it is not used nearly as widely. Most people I know rent directly from landlords, which tends to also mean that they pay one month's rather than two months' deposit. Most found their apartments through personal contacts or advertised in local newspapers.
In support of Bpartner, I can say that they are confident, enthusiastic, hard-working and reply to emails very quickly. As a small company, they focus on customer satisfaction, which most other companies don't seem to consider a priority. Their fees are also very reasonable and I've yet to find more competitive.
Their focus seems to be on brand new apartments, which they usually furnish themselves mostly from KIKA. These are then rented out ideally to corporate tenants at rents which are higher than average. Corporate tenants may not consider price to be their main priority and underground parking, spotless stairways, etc. may bear more significance for them. As a smallish company, Bpartner's apparent market niche of focussing on new apartments for potentially corporate clients makes sense as individuals (younger professionals and foreign students) typically prefer to live centrally in well-furnished, renovated classic apartments in good buildings in V or central VI at more reasonable rents. Individuals who know Budapest well will more than likely not use their services as their suggested rents tend to be so much higher than what is available locally.
I'm not sure if Hungary would concede this or not, but in my experience, Bpartner tends to have less success in renting out the classic apartments that come their way, despite a strong preference for these among younger expats in the city. In my opinion, this is all about having access to the most appropriate target market. I'm not a property manager, but I would have little problem finding tenants for renovated apartments at reasonable prices in the downtown area, whereas I don't know anyone who would rent a new build at Bpartner prices.
Bpartner seem to have found their market niche and I'm sure they will continue to be successful and develop this even further.