For all those that are concerned because the V9 hardware won't support DD-WRT - stop it. DD-WRT supports the V9 version of this router. It really does.

Just go to the DD-WRT site and use the router database search feature and search on TP-Link or something like that to to find the DD-WRT build for the TL-WRT841 V8 version. 

Yes, I said v8. It will take you to a download page for v8. Then choose "Other downloads", then there are folders broken up into years. Then choose the 2014 folder, and look for the latest release date. 

Once you select that, a number of router models will display (which seems counterintuitive, I know) - find the link to "tplink_tl-wr841ndv9". 

That will lead you to the factory-to-ddwrt.bin you need. I installed the 06-23-2014-r24461 package. That is for V9 hardware.

And a few seconds later - wham! A super cheap DD-WRT router. I have purchased a number of routers, and although I use an Asus RT66U AC1750 router mostly in my house, I do have a TP-Link range extender (using powerline networking to feed it) and a TP-Link travel router - and I really like both of those - which led me to purchase this router.

Unlike the Asus, which commands a premium price, the TP-Link equipment seems to lead the bang for the buck category, giving solid, reliable performance for not much money. 80% of the performance of my Asus for 15% of the price.

Anyway, I only flashed the router last week and turned it over to my daughter, so I am not able to comment on the longevity, but I absolutely like what I see so far, and I'm a fairly picky fellow when it comes to these sorts of things. I'm thinking of buying 1 or 2 more for spares. For $20, this is an unbelievable deal.

*UPDATE* 09/26/14
A month or so later, this router still works great. Please note, I recommended this router to a friend, and he had issues, and they came down to simply not doing the 30-30-30 reset when he flashed. You MUST DO THIS. Every router, every flash, just follow the 30-30-30 reset rule (Google it).

*UPDATE* 03/30/15
Router still works great - good throughput, rock solid, never needs to be cycled. One note of caution - my daughter called me and said the router stopped working right around the time she got a new printer. I asked her if she used the WPS feature to try and set up the new printer and she indicated she had. 

Problem is, one button on the back does double duty - press it for under 5 seconds and it initiates the WPS feature. Press it for longer than 5 seconds and (you guessed it) you will enjoy a factory reset to defaults. One of the truly stupid ideas in terms of design engineering. Really, I'm speechless.

That being said, since I've never dreamed of using WPS and would never trust it, I suppose it wouldn't matter to many people who feel like I do about WPS, but it's something to think about.

Also, reference a recent comment, I certainly didn't mean to suggest that you should use dd-wrt version r24461 as an absolute - it was the latest available at the time of my deployment, so it was appropriate to use and name specifically. 

I would think most people who feel comfortable enough to think about flashing their router with dd-wrt would understand that it is somewhat implied that one should start with the latest version of any software (assuming it's in the same release class, not alpha versus RC, for example). The latest version I found for that router as of today is r25697 (dated 12-22-14).