The Good +
GAME.co.uk +9 Love GAME, always receive items well packed and in perfect condition. Would've been +10 other than the fact that twice they have updated their system (to do with card details) without informing me, which has then led to my bank declining the purchase (therefore cancelling my preorders!). First they changed the fact that my post code could have a space, now it can't. And now, they've updated it so that for some reason, my billing address was changed to match my shipping address, which lost me my zelda pre order. Luckily they had one instore for me

So other than that, all great experiences with GAME!
HMV.co.uk +7 Always had preorders early, on at the very latest, on the release date. Love and hate the fact that if you preorder, you get it cheaper than what you would if you buy on release, as it means I always have to preorder things. ALTHOUGH, they only got a 7 because they let me down with the Helghast edition. Paid £100, only for it to be down to £40 within a matter of weeks. Not cool HMV, not cool.
Amazon.co.uk +6 Pretty good delivery times, usually get orders on release date, tend to have pretty good prices. Not much else to say about them?
Zavvi.co.uk +5 Everyone warns people from Zavvi but I seem to have had nothing but good luck from them, items always arriving well packaged and in perfect condition, quite cheap too. Maybe I'm just lucky?
PLAY.com +5 Exactly the same as what I've said above for Zavvi, again - maybe I'm just lucky?
Amazon.com +4 These guys are at the lower end of my positive scale, purely because, I hate the delivery times. I know the items are from the US and the delivery times are to be expected, but on one occasion (okay it was a seller and not actually amazon) I bought the Alien Head CE, and it took over 2 months to arrive. I spent quite a bit on it aswell as it was brand new, and was shitting myself incase I got scammed. Other than that, fairly positive, especially as I have just noticed a nice little refund of customs charges from Amazon as they over charged me for the customs charge when I preordered both the MK editions from them (Kollector's & Tournament).
Neutral -/+
Game4Game.at Got a few preorders scheduled from here, but haven't actually first hand experience what they delivery/item condition upon delivery is like. Spoken to a number of the team on many occasions, great guys (and girls) and due to that, it makes me want to rate them positive, but of course, I'll leave them neutral until I have full info. on what they're really like.
The bad -
None, I've been really lucky so far, although Gamestop pissed me off a while back as I preordered splatterhouse from them, in order to get the splatterhouse mask preorder bonus, only to receive the game without it, and be told I have to fill in a form online - BUT the form was US only. So I couldn't get it. I wish I knew of this fourm then as I could've gotten someone to get it for me then ship it over, but no, I had to sell it on ebay to someone instead. Gutted doesn't even begin to explain how I felt! xx