This place seems to be the only cheap place in Mumbai. The location is amazing, in a central area near the bay, 5 minutes walk to taj mahal Palace, markets and other sights. The staff were helpful and courteous.
The shared bathrooms are new and really clean (not just 'Indian clean') and we're numerous enough that I never had issues with getting to use one. However, the single room was ridiculously tiny, with just a single bed against the wall and a small desk and enough space to move/get dressed. The guesthouse is at the 4th storey so it's a work out to get upstairs, and with the walls not reaching the ceiling, noise became an issue for me when I was trying to sleep at 7pm.
All in all though, for one night stay it's cheap enough that you'll suffer through the tiny room so that you'll be in the heart of Mumbai's most beautiful area.