Not having a body
You'll have to simulate the body and its environment to some extent anyway, because it's the only interface brains really understand. Imagine how terrified many people would be if 1) their last memory involved imminent death 2) they find that they can think but they can't see, feel, or hear anything? And the long term effects of sensory deprivation are not fun. That's without even getting into phantom pains and other super important things like the off-brain portions of the neuroendocrine system (for the most obvious example, spaying/neutering alters much more than just sexual behavior). The brain is not the only thing doing information processing, it's just the main hub.
If you can simulate brains, there is no reason you can't simulate the rest more or less faithfully if you choose. Or for true realism, make a sensory-motor robot body and wirelessly link it up to the brain-hosting server. If you don't do so, you have to alter brain function to make the absence of body-environment acceptable, which generally seems less favorable.
You'll have to simulate the body and its environment to some extent anyway, because it's the only interface brains really understand.
Yes, but I would assume that the simulation doesn't try to mimic physical reality 100%. People probably will be able to teleport around instead of taking a 10 minute walk.
Engaging in hobbies like martial arts or dancing will be much different than it is at the moment.
Look at woman wanting to keep a certain weight to be beautiful to attract a good mate. Look at how guys go to the fitness studio to build big muscles to attract woman. All those physical effects are important for the way our society is made up.
I asked this question on IRC before and got some surprising answers.
Suppose, for the sake of argument, you get cryo-preserved and eventually wake up as an upload. Maybe meat->sim transfer ends up being much easier than sim->meat or meat->meat, or something. Further suppose that you are not particularly averse to a digital-only existence, at least not enough to specifically prohibit reviving you if this is the only option. Yet further suppose that sim-you is identical to meat-you for all purposes that meat-you cared about (including all your hidden desires and character faults). Let's also preemptively assume that any other attempts to fight this hypothetical have been satisfactorily resolved, just to get this out of the way.
Now, in the "real world", or at least in the simulation level we are at, there is no evidence that telepathy of any kind exists or is even possible. However, in the sim-world there is no technological reason it cannot be implemented in some way, for just thoughts, or just feelings, or both. There is a lot to be said for having this kind of connection between people (or sims). It gets rid of or marginalizes deception, status games, mis-communication-based biases and fallacies. On the other hand, your privacy disappears completely and so do any advantages over others the meat-you might want to retain in the digital world. And what you perceive as your faults are out there for everyone to see and feel.
As a new upload, you are informed that many "people" decided to get integrated into the telepathic society and appear to be happy about it, with few, if any, defections. There is also the group of those who opted out, and it looks basically like your "normal" mundane human society. There is only a limited and strictly monitored interaction between the two worlds to prevent exploitation/manipulation.
Would you choose to get fully integrated or stay as human-like as possible? Feel free to suggest any other alternative (suicide, start a partially integrated society, etc.).
P.S. This topic has been rather extensively covered in science fiction, but I could not find a quality online discussion anywhere.