So basically, at current Ixcoin difficulty, in the time it takes me to mine 1 Bitcoin, I could mine about 1000 Ixcoins and sell them for about 2.4 Bitcoins.
Nice...if that is true, then it should get arbitraged away *very* quickly. I think if I had any IxCoins I'd want to sell before that happens. It's not too often that you can more than double your mining yield like this (but again, it's probably a good idea to act quickly).
It's not any different than the brief periods of time where namecoin is more profitable than bitcoin, really. Check out
http://tvori.info/bitcoin/charts/ if you're not familiar with this phenomenon. Specifically go to the "all time chart" at the bottom and watch the relationship between the green line (BTC profit) and the blue line (NMC profit). If we had several more popular and well-known forks we might see network hopping as widespread as pool hopping is today. As long as you can determine (in real time) the BTC value of NMC/IXC/whatever and the difficulty of each network, it's trivial to determine where your GPU will make the most cash.
For the record, I do expect the profit differential to be arbitraged away quite quickly, but we probably won't see a stable exchange rate until we see a stable difficulty. Every increase thus far has been a factor of four (currently at 4096) and block times have been well under a minute. With the exception of the brief times when NMC mining is more profitable, NMC seems to have a stable value of 0.03 BTC or so, meaning that it's usually worth about 68% of what you'd get for the same time/equipment mining BTC. We're still in the "initial climb" phase of difficulty with IXC, but I'd expect a similar result once the initial climb is over.
Only time will tell of course.
As for the "value" IXC adds? I'm not so sure that too many exist, certainly less value than namecoin - but one look at the trade volume on bitparking's NMC exchange compared with the actual number of .bit registrations should tell you it's as much a speculative commodity as bitcoin. Speculators in NMC are betting that its potential as a DNS replacement will make it more valuable in the future, and with IXC the bet is that hitting a deflationary curve earlier than BTC will increase its relative value as it will be deflating while BTC is still inflating.
If nothing else, trading BTC for IXC or NMC and then trading them back goes a long way toward anonymizing non-generated BTC since the IXC and NMC exchanges don't deal in regular fiat and therefore don't care so much about who their customers are.