[Bonafone]

I do believe there is a huge difference between these levels. I played over 2500 50's and have logged about 750 100's and I think the play is definately tougher.

At the 50's I would often browse the internet and talk to numerous friends while playing without really feeling a difference. This may just be me but I need to focus a lot more at the 100's and get some reads to be successful.

Also I think at the 100's many of the players will exploit your weak plays. EX: with a 1300 stack in level 4 i could often get away with a 275 raise because the players in the 50's wouldn't come over the top of me as much as they should have. But at the 100s you will not get away with this enough and people will constantly exploiting here. So what happens (at least with me) is that I will push with a bigger stack.

Also at then 100's more people will be stealing blinds, which means you will have less opportunities to steal them yourself. This means that it is important to always look hard for opportunities to steal, because you can't afford to miss your opportunities.

As to your ROI question I think it should be known your ROI will drop. How much it will drop will depend on how well you adjust. I've found I place 8th a lot more in the 100s then i did in the 50's, but this may be due to me trying to acquire chips earlier.

Hope this helped, feel free to PM any other questions you may have.