I stayed in Hotel Sylvia from Aug 7th 2011 up to Sep 10, 2011. The location is very close to istiklal jaddasi, a 20 minute walk from Taksim, and just a few meters away from shishhane metro station. The rooms are so simple and clean. They have shower, TV (with satellite channels). The staff who can communicate in a lame English are nice and friendly. The breakfast includes bread, jam, honey, cheese, tea, tomato and cucumber slices and a boiled egg.
I don't know the rank of the hotel, but I used to call it a star-less hotel. It has high speed internet connection as well.
If that's important to you where the location is and you just need a clean place to sleep and you want a relatively low-budget hotel, then go to Sylvia Hotel. Aha, BTW, I spent 70 TL for a night and when my husband joined me, it increased to 100 TL. They told me for a three bed room (which most of the rooms are!), they would ask for 150TL.
To conclude what I said; you shouldn't expect much. It's clean and nice- that's it!
