Ahh it looks like I've got that speed issue too on a 2820 - for people that are seeing the speed problem, is it when using a PPPoE connection on WAN2? Because that's what this setup is using and seeing exactly the same kind of speeds as j.baker.

I download a beta from

ftp://ftp.draytek.pl/Seria_2820/Firmware/

USE AT YOUR OWN RISK

Neither I or Draytek will take any responsibility if you flash or encounter any problems.

No speed issues in 3.3.5 beta.. working well here.

3.3.4.1 must have some odd bug.. I wish draytek would get some quality control and test their firmwares.

I can also confirm a severe drop in ADSL service performance since the upgrade. My broadband is delivered using ADSL MAX.

When I am using firmware version 3.3.4, speedtests hit 7Mb. With version 3.3.4.1, speedtests hit 1.4Mb maximum. A roll-back has seen a complete restoration of speed.

I can also confirm the speed deterioration is not present in the BETA version (3.3.5).

(However, I had to disable the firewalls for the BETA to work due to not understanding the Session Limit configuration needs within the new version if anyone wants to point me in the direction of any release notes....).

I've found by reducing the MTU down to 1458 on V3.3.4.1 firmware my DL speed is back to normal. Tried other routers and tested ok at different MTU rates.