Uberman,
Here's my thoughts, and my answers to your questions...
Unfortunately, I don't own a fleshlight

, so I used my hand. I do want to get a fleshlight though.
Was it too easy/hard?
The beginning was a little easy, but as-is it was a nice warm-up
Was there certain parts that were crap/impossible/hard?
I wouldn't say that it was "crap", but feel that one area needs work. That area is the "Edge" which ends each round. Several times during the tease, I could have lasted longer. Instead, I hurried to the edge, so that I could progress to the next gal. Perhaps it would be better if, during each "round" (not the intermissions), you had to have the stamina to survive a count-down clock (such as a 5:00 first round, 10:00 in the second and then 15 or 20 in the third. However, as I've got no experience with a fleshlight, lasting my suggested times with one might be downright impossible...I don't know.
Was the timers too long/short? After the third round, I could have used more rest. I'll admit though, that I hurried through the doors. That said though, I survived. As is, the tease becomes mildly challenging as it progresses, which isn't necessarily a bad thing.
Some other thoughts...
Nice variety of girls, and good image selection. Even when images repeated, I took the opportunity to stare at other parts of their bodies. I favorited the tease, will definitely do it again, and I definitely want to try it with a fleshlight someday.
Almost forgot: Didn't have any "accidents", and I opted not to cum; will be spending the rest of my evening horny & frustrated.
EDIT: Loved the Faster/Slower buttons. Great idea!
This boi enjoys having to ruin his orgasms. Also, do this boi a favor and force boi to lick up his nasty jizz.