Basically, my formative RPG years were first D&D (Basic & AD&D, but then lots of focus on AD&D 2nd with regular groups) and Champion (now Hero System). Played some TMNT and Other Strangeness, M&M, V&V, Marvel (FASERIP) and other 80s/90s supers, which were generally more D&D-like than not.
Funny how much all of those (barring Champions and FASERIP) show the DNA of D&D in their designs, isn't it?
So if you can share your experiences with Sentinel Comics (or any others like ICONS), I would appreciate it.
Unfortunately I haven't really done anything like session reports, and while I've got a series of posts planned talking about play expectations and system strengths and weaknesses they're not even in rough draft format yet. You might find the blog posts on
this index page somewhat useful for getting a feel for game mechanics in practice but it's not really what you're asking about.
In broad terms, I'd describe the game as fairly rules-lite, with the actual gameplay explained in about 32 pages including examples - less mechanically complex than V&V, more so than Masks - with most of the complexity sitting in character creation (akin to M&M or Champions, but with considerably fewer decision points and very little math involved). There's a strong focus on "action scenes" which is a game term for any situation where there's some kind of time pressure involved - often but not always involving combat, and without a set turn length so you can do some innovative stuff with the system like (say) running a political campaign over the course of several months of in-game time as a single extended action scene. There are also "montage scenes" which reflect prep, investigation, and recovery opportunities and are usually light on die-rolling but advance the story toward the next action scene, and "social scenes" that are more or less pure roleplaying with few or no die rolls involved - and can be purely between PCs if desired or involve NPCs as well, which is good for developing your character personalities and have a small mechanical benefit (everyone involved earns a hero point, giving you an edge next session).
Character design has (technically) three approaches, each of which proceed through the same eight steps (one of which is just finishing touches) in slightly different ways. Which approach(es) you use is usually decided on by the GM or the whole table, and IME it really doesn't break anything if different players use different approaches. "Guided" (as in: by the dice) is the randomized system, where you roll several dice and choose some of them to make decisions in the current step, then roll more to determine your options for the next - this is best for beginners (it has the least decisions to make) but also useful for inspiration. "Constructed" removes the randomness and just lets you choose how you proceed through each step, at the cost of adding a lot more decision making and having some potential for analysis paralysis - but it's also good building to a firm concept, and some people just hate letting luck decide anything in character gen. The "secret third option" is rarely used IME, and essentially throws most restrictions out the window in the interest of letting you build whatever you want - which obviously could have some serious problems with cherry-picking, but should let you create even the weirdest character concepts. The fact that a good GM-player team can make the third option work with some careful compromises says something about how tough it is to seriously break game balance.
It's hard to speak about what a "normal" game session looks like for everyone, but IME a 5-8 hour weekly session with 3-6 players who were all comfortable with the system would normally see 2-3 action scenes interspersed with 1-3 montage scenes and as many social scenes as people were comfortable with - you don't have to be in a social scene to roleplay, and one can end abruptly if the situation calls for an action scene breaking out as someone attempts to murder their conversational partner. From teh GM's side of things your prep pretty much consists of coming up with some events that might happen - usually but not always driven by villainous schemes - and planning out action scenes to support those events. There's some stuff on that blog link about my approach to designing action scenes, but I probably didn't emphasize that doing improv to create is pretty easy once you know your players styles and have a few baddies handy to pull from - there's literally hundreds of villains on my blog, and thousands of fan-made ones online.
Oh, and one critically important thing - despite the name and at least some of the designers' desires, there is no need whatsoever to confine yourself to playing the SCRPG in their universe. Works just as well as Champions, M&M, V&V as an engine for playing your own homebrew setting, and can be adapted to published real-comic settings pretty easily. If you want to use the canon setting the book covers it fairly well and there are hundreds of podcasts from the creators fleshing it out further (although maddeningly most of the content is pre-RPG timeline, before their faux-publisher's equivalent to DC Crisis on Infinite Earths reboot), but it sure isn't mandatory.