Honestly, with the recent updates to the monster math, Paragon plays a lot like Heroic. This is coming from the perspective of a player, not a DM, but currently playing through Scales of War with my group, and combats seem really similar to Heroic-tier combats. The monsters put out enough damage to make us sweat, but we usually manage to pull through, unless denied short rests or a long stretch without an extended rest... at which point we really start to sweat. Or party is rather leader-heavy, though, with a Warlord who loaded up on the Fight On feat to get four uses of her Inspiring Word each combat, and my character, who is a Defender/Leader Hybrid, who can dish out a little (but not much) healing and defensive buffs. Parties without Leaders, or with only a single not-so-effective Leader, likely could not have made it through some of the stuff we have.
General thoughts on Paragon, though:
-PPs usually give players extra stuff for using an AP. They can combine this with feats to really 'optimize' AP usage. Action points become a much more interesting and important resource. Be careful how you dole them out.
-Monster math fixes made monsters threatening again. My level 18 Swordmage/Artificer fought a combat recently where the monsters were routinely doing 50+ damage to him. He barely managed to stay on his feet, and lost half his surges that fight. Point is, whatever issues there may have been with Paragon play in the past (and I'm sure there were plenty), they seem more or less fixed. Monsters are dangerous, but can be bested. Just make sure to update those old MM1 and MM2 paper tigers.
-PCs have easier access to significant status conditions, like Stun or Dominate. Others can hand out Dazed like candy. If you're going to have them fight a Solo, try to give them some way of compensating for status conditions like this, or else risk having them utterly trivialized.
-This might just be from playing in a party with both a pretty good lazylord and a character that's half artificer, but I've noticed that my party can throw out insane buffs. My guy can give an ally +3 to attacks and +5 to damage for an entire encounter. The Warlod hands out +14 damage with an AP. Double-check your player's powers to make sure they aren't stacking bonuses illegally (ie., two different sources of "item" bonuses or "power" bonuses).