Here's what I'd do:
First,
Leave the multimedia class scheduler service running, but disable its network throttling "feature":
- Open regedit
- Go to: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile
- There will be an entry for network performance throttling, default value is 10; set it to FFFFFFFF hex (willl look like 0xFFFFFFFF to the right of the entry)
- Reboot
This has made a noticeable difference for me in terms of ping stability.
Second, defrag. I'm assuming you've patched to the latest version, which means your game files are now fragmented.
Third... allow Punkbuster Admin rights. If you're running a 64-bit system, then go to Windows\SysWOW64 and give PnkBstrA and PnkBstrB admin rights. Then head to Program Files (x86)\Battlefield\pb and, if it's there, give PnkBstrB admin rights.
The 32-bit version's files can be found in the System32 folder. The game's files are just in Program files... no (x86) folder.
If you've got anti virus, then I would deselect Battlefield from the real time scan.
If it's EA's master server just being slow to respond... which is actually a common occurance... then there isn't anything you can do about it. As you say, once your past this initial pain, the game runs fine, right?