I moved into a flat let by Rainbow Properties last September (2011). Within weeks, the hobs, suspicious to begin with, failed to heat. In a studio apartment with two burners and a microwave, this made any kind of cooking difficult. It took nearly a month for a replacement to be installed.
When the cupboard doors rotted off their hinges, I was sans requested updates for weeks before the problem was resolved.
In the beginning of March, the microwave began bursting into flames upon use. Now midway through June, the dangerously defunct microwave is still here, posing a serious fire hazard. Multiple follow-up messages were entirely ignored by the estate agents. I did not receive any replies until after I gave notice that I intended to leave, but the agent's non sequiturs never addressed my two major issues: that I was blatantly ignored, and that the microwave is dangerous. (You can find a neat clip on YouTube of the microwave's magic trick if you search for Rainbow Properties + microwave.)
If you don't mind an unresponsive landlord who is not afraid to violate your lease agreement, go ahead, and rent with Rainbow Properties.
(As an interesting note, I looked up Rainbow Properties' listing of the flat I am renting, and saw that they advertise it as being located in a "new build building [sic] built last year", which is outrageously false.)