Ok, i've read all the posts in this thread, both Reece and Lorenzo make valid points but here's a cheapies perspective.
Today a quad premium LLLL.com = $450. Following the LLL.com and LLL.net scenario, quad premium LLLL.net should be $45 each. Currently available for reg fee. Bad investment, I think not. I can't for the life of me see a 'loss making' scenario. Even with 2-3 yrs of reg fee in the fray.
Now this premium domain available scenario in LLLL.net is changing as you read. I first even considered these when LLLL.com prices went ballistic beginning of this year. There were 15k premium .nets available sometime after that. Cut to feb 3rd - there are now 2k or less. Thats actually less than 15 days.
????: NamePros.com http://www.namepros.com/short-domain-discussion/425853-main-reason-why-llll-net-may.html
Granted that LLLL.net might never sell out (though I guess they must have said the same about LLL.net) but at least the premiums present an entry level opportunity which no longer exists for LLLL.com
And there are a LOT of companies in technology and other related fields who'd prefer a premium LLLL.net to a 'bad' LLLL.com specially when the price difference between them will exist. This is my target market and who's to say $6x3 today won't be $1000 in 3 years.
I'm hedging my bets, gamblers, stock brokers and other financial field people will understand what I mean. When I first got the 15k list, I bought 10. Then I shortlisted 100, went to take 10 more, all 100 are gone

So I found 33 more I like took them, shortlisted another 100. Went to take ten, ditto. So I found 10 I liked and registered those.
Fact 1.
Premium LLLL.net - 2k left, you can jump in now at reg fee or buy them from domainers who did... if they sell.
Fact 2.
Granted premium LLLL.com = min. $450 now, $1k by end of 2008, maybe even $2k by end 2009. At 10% I'd be willing to sell my premium LLLL.nets then.
Fact 3.
A new company, specially a tech oriented one, is more liable to pay $500 for a .net (Spot on smashfactory) than $5000 for the SAME .com, premium, not premium, notwithstanding.
So do I recommend you sell the house and buy these, NO. But do I recommend you buy enough to cover 2-3% of your portfolio as a long term hedge fund, absolutely.
Though, with the speed these are going this whole discussion will be a moot point in 2 weeks. Then we'll have the same discussion for non-premium LLLL.nets