I didn't stay at Bally's so I can't comment on the rooms but I did spend a good deal of time in their casino.
My favorite casino on the strip. Why? Because they are who they are and they're not trying to be something they're not. They're not shiny or new. The Cosmopolitan this is not. The waitresses are a bit rough around the edges and look like they probably work a second shift at some seedy dive bar off the strip. They can't pull off the tight revealing uniforms that you see the much younger girls wearing at the newer casinos. And that's ok, well at least for me it is. I don't care what you look like as long as you keep the (free) drinks coming. I went here early one day, maybe around 11am and our waitress was so on the ball. She'd plomp a drink down in front of me and be back in less than 5 minutes to ask if I needed another one. My drink was as full as when she left it but gotta love that initiative!
Another biggie is that they're one of the few casinos that do $10 minimums as opposed to $15. This can make a huge difference.
Also, wut up to Michelle at the roulette table. She was awesome and I had the quintessential beginner's luck gambling experience at her table. I think I had at least a 20+ win streak going on and it was the best time ever. My first time ever gambling in Vegas and I walked with $240 that night. Not bad for a rookie.