I have a DIR-825 and I tried dd-wrt with terrible results.
I started with a DIR-825 rev B1 with the stock 2.02NA firmware.
I installed dd-wrt following the directions, and it seemed to work and I could configure it with the dd-wrt web setup, but I had no wireless.
So, I flashed back the stock 2.02NA firmware, and reset it to factory defaults. Now I could get into the web interface of the stock Dlink firmware... but still NO wireless! The wireless LED's would not even turn on.
Next I tried putting back dd-wrt, but now, if I flash dd-wrt onto the router, I have NO network at all. I can't connect to dd-wrt at all, via LAN or WAN ports, and there is no wireless. I can see that dd-wrt is booting, because the little world icon LED lights up that sickly purple color that only dd-wrt does when it boots.
I can still flash back the stock firmware, or I can flash on dd-wrt, or even OpenWRT, but I have NO wireless in any of these firmware. It's like the wireless is broken now.
When I tried OpenWRT I followed ALL of the suggestions from this thread. I thought I had the same problem that LuisGC described in this thread, except he was able to sold it, and I couldn't.
LuisGC says he got wireless fixed on OpenWRT like this:
1. Flashed router with the latest 'openwrt-ar71xx-dir-825-b1-squashfs.bin' build
2. Did the 30/30/30 hard reset
3. Connected and installed the hostapd and kmod-ath9k
I tried to follow those steps, but I could not use the file "openwrt-ar71xx-dir-825-b1-squashfs.bin". The emergency flash page (accessed by holding down reset for 45 seconds) always says it has the wrong hardware ID. I could only use the backup loader version, which i got from here:
http://downloads.openwrt.org/snapshots/trunk/ar71xx/openwrt-ar71xx-dir-825-b1-squashfs-backup-loader.bin
So I used that version of OpenWRT, did a 30/30/30 hard reset (which in my experience doesn't seem to work right on this router), and I installed the packages hostapd and kmod-ath9k.
Still no wireless! I could see that the ath9k module was loaded but no wireless.
I couldn't add the radios with Luci because Luci is broken on the OpenWRT image I used. It just returns at error "Not Found" when I browse to it. Sigh. I found a thread that says this is a problem in the sources of this build or something. So I manually edited the wireless configuration file, using the settings I found in this thread. Still no wireless. The wifi detect command reports it can't find the radios.
I wanted to check my system logs for the error other people saw about symbols, but didn't know how, because I don't have Luci working and I don't know where that log resides on the system.
Also, someone said they used the command "erase nvram". I was never able to try this on my router. Why? Because that command doesn't work for me when I'm logged into openwrt, it says there's no such command or something.