A lot of folks feel that Hollywood simply cannot make great television, 26 episodes a year. It is too expensive to maintain the kind of writing and production activity that would be necessary to do that and achieve high quality, so 13 episodes (as we'll see for both Heroes and Chuck next season) is a good thing: Writing and production staff can focus their 13 best ideas into the series, and leave the chaff behind.
Regarding Leno, I jokingly refer to it as the Scourge of Leno. It does take five hours of prime time out of contention for a scripted drama; I would personally prefer the dramas to a variety show. However, I don't see how it could hurt the network: Remember, their objective is not to win the time slot (although, perhaps they could). Their objective is to make profit. Leno costs about one quarter of the least expensive scripted drama, so effectively NBC "wins" if their advertising revenues are any better than 25% of that of the show that wins the time slot.
Do be aware, though, that those aren't the only five hours being "lost" in that way... The CW has decided to cease operations on Sunday night. They actually had a five hour schedule on Sundays (5PM-10PM) though it began with mostly reruns... still there are a couple of hours of scripted programming that simply won't be programmed next year. So the overall amount of scripted programming is decreasing, a clear reflection of how much the original programming on TNT, USA, FX, etc., and on HBO and SHO are successfully stealing audience from broadcast networks.
To be fair, though, as I think I mentioned earlier in the thread, after looking over the plans for the fall very briefly, I've concluded that there is just as much interesting programming planned for next fall as there was last fall. Perhaps Leno just focused NBC's attention regarding scripted programming to the 16 other hours they had to program (and, of course, CW's programming on Sunday is no great loss).
NBC won't have to tone Heroes down at all. The time threshold for programming standards and practices is 10PM, nationwide. And since all the networks broadcast the same show from 10PM-11PM Eastern at 9PM-10PM Central, effectively the rules have been that all primetime shows must comply with the same standards. It has been like that for years. The whole "family hour" thing was voluntary to start with, and didn't last long, because it wasn't profitable. For years, now, there have been many shows that have been broadcast before 8PM Central Time that are clearly not intended for children, i.e., How I Met Your Mother, with all its talk about casual sex and how drinking in a bar is so much a focus of the show; The Simpson (need I say more?); NCIS, with its depictions of violence; Reaper, which actually featured a consummated story-arc where a main character lusted after his step-sister; Big Brother, with very clear insinuations of sexual promiscuity taking place; etc.
