The bionic arm swing mechanic takes some getting used to, of course, but you learn to live without a jump button (or you get frustrated and quit playing). The game at times demands an incredible amount of precision in your grappling, but for the most part that stuff is confined to times when you are hunting down optional secrets. However, you can really feel yourself getting more and more skilled at flying through the levels grappling from one place to the next, with your feet only hitting the ground when necessary. This is what made Bionic Commando so unique and awesome 20 years ago, and keeps it so to this day. I hope the 3D 'modern style' Bionic Commando game feels this cool.
I finished the game tonight--on easy mode, because I value my sanity--and managed to find every piece of equipment, and every little cleverly-hidden secret, so far as I can tell. There are a couple of blanks left in the database, but I'm thinking those are unlocked by stuff you encounter on the higher difficulty settings.
There are two distinct areas to BCR's challenge factor, a) the environment itself, and b) the enemies. The stages are more or less identical on easy, though there are some phantom safety platforms provided over pits and spikes from time to time, especially in the last two or three stages. Where it feels like there is a ton of difference is in the enemies, the bosses in particular. Most run-of-the-mill enemies died with just a few shots, and the bosses were all extremely easy. Most of them I beat two or three times, since I was running each stage several times to root out all of the secrets. I get the feeling that on hard or super hard mode, these bosses could be incredibly cheap, whereas the stages aren't going to change all that much.
If you're looking for a good challenge based solely on the terrain (or lack of it) you have to navigate, there are the 60+ challenge rooms you can attempt. I've done about 9 or so, and already they're getting into Braid territory where you'll look at it and think "how in the fuck?" Good stuff. I've already pulled off a few maneuvers you'd think impossible at first glance.
All in all, BCR is great. If you liked Bionic Commando, you'll love what they've done with it here. If you're new to it altogether, try the demo. I can see the uninitiated being thrown for a loop to begin with, but it really is worth it to stick with it until you've got the hang of it, so to speak.