Misunderstood Clearances

We have miscommunications rarely, but they do happen. One thing I find interesting is that there is a new trend that is a bit alarming. We have better radar coverage than ever before. In the past, due to the lack of radar coverage, we had to work more non-radar, or procedural, separation in our environment in Moncton. That gets more complicated in many respects, as we have to ask pilots for DME, altitude, radials, etc, and in many cases, assign pilots restrictions to prove separation. A simplified case of a clearance to a departure could be something like, and it's a perfect example, out of Saint John, NB:

"... maintain FL280, depart runway 32, climb runway heading to intercept V314 and proceed on course, not above 4,000 til MOWND."

MOWND is an intersection on V314 about 30NM west of YSJ. The reason for such a clearance could be, perhaps, someone transitting northbound on V310, an airway also off YSJ, and this 30NM restriction would keep our departure under the enroute airplane until they are geographically spearated. This is a lot less complicated than some we used to issue, and rarely ever had pilots misinterpret. This is also an actual clearance given to a Jazz RJ not all that long ago (the tapes are long since gone, so he can't be incriminated now). Anyway, the reason I bring this up is because the pilot departed and flew the assigned route and climbed to 4,000. I was extremely busy during these particular moments and was unable to return to the aircraft to break his restriction and let him climb earlier when I saw him on radar. Since safety was assured by the clearance, my attention was briefly focused elsewhere. When my gaze returned in his area, he had long since passed MOWND and was still at 4,000 feet. Just as I went to ask if everything was OK, wondering why he hadn't started to climb after passing MOWND, he made a transmission: "Moncton, Jazz One Two Three Four when can we expect higher?"

The restriction was a self-cancelling type. Immediately after passing MOWND, a non-compulsory reporting point, the aircraft was allowed to climb to FL280. The pilot was told that, and he said he wasn't sure what he was allowed to do. I have a problem with this. If the clearance wasn't clear, why did he not question this on the ground before departure? I'd much rather have a pilot ask for clarification of a clearance than have him fly a clearance wrong. This is happening more and more often, and mostly with airline types. I think there are too many pilots expecting terminal service at airports that have a complete lack of terminal-type facilities to provide them with such services. Still, haven't many of these pilots done time in smaller airplanes (like the much maligned Navajo) into and out of these smaller airports in the past while building time? I wouldn't expect this kind of clearance to be completely unfamiliar.