Well, their games are still brilliant, but there's a few things in which valve seem determined to piss everyone off.
L4D DLC given no TLC
Just getting this out of the way, I like the L4D series, and I think L4D2 just had enough improvements to warrant it's release so close to the first game at full price. Debatable, and I know many people who like L4D more, which is fine, even good, it'll keep the first game's community alive. BUT! the problem comes in with DLC. When they announced L4D2, they promised to keep DLC going for both games, thus keeping both communities alive with new content. But they have so far been rather lacklustre in this, with the passing for L4D2 coming out months after it was supposed to, and god knows how long it's L4D counterpart, "the crossing" will take to get out. Sure, mutation serves as a nice way of keeping people coming back to L4D2 without constantly releasing DLC, but if they plan on producing new DLC as a way of boosting players, they better start being more consistent about it and stop taking nigh on a year to produce only a three-part campaign.
"Everything's on track...to release in another two year's time."
Valve seem to have a few chronic procrastinators on the team, as valve have a terrible history of delays. The passing was a textbook case of valve time. Before L4D2's launch, they said they'd have it out within the first few months of release. They didn't. When it had a release date, they left it up until that date to announce they'd be taking another couple of months to...Well, god knows what. And let's not even get started with HL2 ep 3...
"Portal-themed announcement"
You may have heard that after speculation of what valve's big E3 announcement would be, they announced it wouldn't be portal 2, but something portal-themed. I swear, if they have a "portal" set up, and the L4D3 characters walk out of it, there's gonna be trouble...
Valve dates PCs
valve have an almost unfair preference towards PC players. Whilst PC TF2 has been updated constantly, console versions have recieved nothing, which I can almost understand, technical limits, blah blah, but the servers for the 360 version have been allowed to fall into disrepair. Laggy games are all too common. Modded games allowed to spam up matchmaking. What's more, there's gaping exploits a plenty. All too often, a game has been ruined by engineers UNDER the map. Seriously valve, if you could kindly take time off from making out with the PC crowd, how's about fixing some of the exploits at least, hey? Maybe just chucking us even a slightly improved connection?