I can not believe the level of moaning and complaining that has been going on in this forum. These companies are offering extra content for FREE, and you are all acting as if they've done something terrible. Think, there are two ways things could have happened...
1. No-one offers any bonus pre-order content. You pay for the game, and get the standard 18 civs and no bonus maps. When the DLC is released, those who want it buy it, those who don't think it's worth the money don't.
2. Retailers decide to give bonus's to those who pre-order. You get the same stuff as above, however you also get something additional FOR FREE.
Things like this happen all the time. I got interested in StarTrek Online before it launched (it is terrible by the way), but they had a similar system where some retailers would offer a unique costume if you pre-ordered through them, others might offer a new race to play as etc. And everyone on their forums thought it was great. There were threads where people would discuss which one they were going to go for. People would way the pros and cons of each deal. You get to pick something that would be a cool addition for you, and (yes i feel i have to repeat myself again) you get it FOR FREE. The alternative? You get nothing.
Now, to continue my example, there will be no compatibility problems at all. If you chose to buy the deluxe addition for Babylon, but your friend didn't, you will both be able to play together. The difference? You will have the option to play as Babylon and he won't! It's as simple as that.
As for missing out? Anything that is DLC will be available to everyone eventually.
As for non-DLC bonuses, nothing company specific will be important enough to get worked up about, because the developers know that no-one wants to buy multiple copies. Company specific stuff will be map packs and minor stuff, no full Civs, nothing to really miss.
The only non-company specific, non-DLC bonus is Babylon. It will not necessarily be offered at a later date, because that would make buying the Deluxe edition pointless and be unfair to those who did. But no-one has to miss out, because everyone has the option to buy it, and every retailer that sells the standard game will almost certainly also sell the Deluxe edition, along with their own company-specific promotions.
The bottom line is:
-If you like Civ5, buy it, if you don't think it's worth the money, then don't.
-If you believe that Babylon is worth an extra $10 to you, then get the Deluxe edition, if you don't then don't
-If you really like the offers a particular company is making, then buy it from them, but in the long run it's really not likely to matter at all.
-Stop whining like a bunch of little girls.
And don't even get me started on all the pointless complaining about Steam...
Moderator Action: Flaming - warned
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