I stayed in the Regency Inn on the back of a 12 hour train from Goa. I was happy to get my head down here for one night and then move on to other areas of Mumbai.
In general is cool for a traveller, it took me back to my backpacking routes a little. The rooms are ok, but not very clean apart from a decent lick of paint. The noise is pretty harsh from the main causeway, and the beds are rock hard with not much of a pillow.
Apart from that the staff are really kind and helpful, and the location is spot on. It is located right in heart of Coloba, close to restaurants, bars & the hussle and bussle of the city.
If your on a tight budget, go for it. If your looking for a bit extra, your own bathroom and a decent bed, look elsewhere!