Lurkers are really great peeping toms.
Er... ah, yeah. Lurkers are actually my favorite monsters, but the most under-represented role.
I feel that Lurkers should evoke one of two responses. "Help! It's on me!" or "Ow! Why you little - come back here!"
One trick to really zazz up their presence is to hold onto them. Many lurkers have powers that let them stay undetected, either via invisibility or stealth. So wait for the most opportune moment to bring them out in the combat: usually in the middle, against someone who was just bloodied, or a controller.
If want to use them out of the gate, or give an idea that they are there, let them attack once, and then go into hiding. Letting the PCs know something isn't right. For instance, several lurkers have the "If you miss with a ranged attack, you stay hidden" power. So I would actually narrate in the opening round or so, "A crossbow/dagger/heat seeking bolt of magic whizzes by your nose from x direction, but you don't see the source". This way the PCs know something's up, but they 1) can't see it and 2) can't get to it.
Your lurkers can play protector. Have one hiding by an artillery or ranged controller. Someone is eventually going to come after that artillery or controller; and when they engage it in melee, the lurker pops up behind them, uses its readied action to hit them, then run. This is especially true if the PCs have some sort of objective beyond "kill all enemies"; the lurker is protecting the lever to be pulled, an obviously displayed item, etc.
Additionally, when they pop up, it could involve some sudden reveal. Maybe they were lurking in a trap door/secret passage, and now that trapdoor is open, either to push an enemy into, or to explore later. Maybe they release a trap as they enter - dropping a portcullis that divides the players, for instance.
Finally, for some lurkers that grab and do bad things, consider using snatch and drag methods. The bugbear strangler doesn't just stand out in the open with his strangled victim; when he sustains the grab, he drags them around a corner or into a trap door. This will up the ante for PCs to address the issue.