Don't jump and buy it yet. At 8PM GMT the new digital distribution company Get Games, co-founded by the Eurogamer Network and Mastertronic's Andy Payne, will launch and Serious Sam HD will be 10 pounds.
More info here.

Ugh another game I will skip over then. This is starting to become a frequent occurance which as far as I'm concerned is not good.

Seems that the download from Get Games won't be tied into Steam.

It will be a great web shop I think. Do anyone knows the link of the Get Games site? I know it will be open this evening but I couldn't have any link for it. Just found this pic.
http://www.twitpic.com/qoq9v

It's http://www.getgamesgo.com/

I assume this thread is a pretty good candidate for early info.

It is using ActiveMark, it is worse than Steam and has limited activations AFAIK?

I'm not impressed Activemark. According to the rule enforcements you never actually own a game there is always a time limit which means if you have no access to the internet then eventually even a game you purchased will revert to a trail version if it cannot dial home.

Hm, conflict of interest maybe? I still expect Eurogamer to be fair and unbiased in their reviews, but what about their news coverage? The shop will apparently sell classic games as well (so it's competing with GOG). I hope this won't make them reluctant to post news about GOG-related stuff in the future.

They say that they'll keep things unbiased
Taken from Games from the Get-Go Interview.
Now we can only see if they'll truly be unbiased or not.
Just bought the game and you need Steam to activate it and play it. You have the option of downloading the installer from their website and afterward associate it with your Steam account and install it via that file or just add the cd-key directly and download from Steam.

Yeah, we'll see.
It is interesting that, due to the Mastertronic/Sold Out-partnership, this could actually become the most serious competitor GOG has to deal with in terms of classic games. Mastertronic have published a small number of indie/new games, other than that they're all about budget rereleases. Pretty much like GOG, only retail-based.
I assume they can't just take the entire catalogue online but they've got distribution deals with just about everyone and have published a huge amount of classics over the years, so they're not starting on scratch here. Though they probably don't have any compatibility-solutions yet.

Hmmm...remake that really harnesses my flagship system, or the already tried-and-true Serious Sam Gold that runs on just about any computer made in the last few years like butter, hence increasing my opportunities for co-op play?
*also makes note to scour eBay again in hopes of getting SS Gold without fucking up on the bidding this time*

I've always liked the idea of the gameplay in Serious Sam more than the actual execution. It's fun to shoot all the hundreds of enemies onscreen, but the developers just do it with lack of style and polish in pretty much every aspect of design. The animations are subpar and uninteresting, sound effects are weak, character models and design are amateurish, and the environments are just big open areas with no interesting flow or visual appeal at all.
And from what I've seen in the trailer, looks like not much has changed. Despite all its shortcomings though, I still might pick it up after a price drop.

There's always some monster hunting in Unreal Tournament if you don't want to drop the cash right now.

No shit... there's this awesome mod called The Haunted for Unreal Tournament 3. Its gameplay is heavily inspired by Resident Evil 4/5 but without the stupid limitations. You can shoot while moving, do dodge rolls, and jump. As you fight waves of increasingly powerful enemies you gain experience and earn new weapons. There's even multiplayer coop. It's good fun for anyone who has UT3.