I was with DD-WRT for several years. From a vendor to a custom FW, it was day and night. The customization, granularity and features not available on the vendor FW made it great.
But lately, I found that for a medium user, It was more difficult to keep rolling with DD-WRT. For those with an Atheros device, I think that maintaining the FW is the job of one guy only (Brainslayer).
Also, the documentation is a hard to roam on. The router database has been obsolete since I don't know when, the wikis are not always updated and the CLI is all with swconfig which is not easy for the profane.
I wanted to convert a router into an AP but with two SSIDs handled through 802.1q by pfSense. On DD-WRT, that would have been really hard for me.
I decided to give OpenWRT a try and it worked. I am glad I did.
I can't say I did not tumble on any discrepencies but I did what I wanted to do and I understand how I did it.