I picked up a Nissin Di866Mkii recently. If you search online, you'll find it in the low to mid $200's. Compared with the Yongnuo's, it offers high speed synch which might be an advantage if shooting portraits outside. And, although it is only marginally cheaper than a 430exii, it is a bit more powerful. On the down side, it feels a little flimsy and emits a crackling sound (but no worse than the high pitched noise of other flashes). So far, it has done the job well.
My other flashes are non-EX Canon flashes (old Canon, Minolta, Sunpak). I use these in auto mode (via thyristor) or manual mode when they're on the hotshoe. When I go wireless, I use an el-cheapo Cactus V5 wireless transmitter. With a set-up like this, it doesn't really matter what type of flash you use as long as you have the ability to manually adjust the flash power. Some older Canon flashes (eg those ending in "EZ") aren't compatible with exposure modes on modern DSLRs. But as mentioned above, work perfectly in "Auto" mode or off camera. And they aren't that expensive on ebay. But the downside with going cheap is that you need to spend more time setting things up to make sure the lighting is perfect. You can never be sure that an improptu shot will work out. Not a problem for an amateur like me, but would be really annoying if doing things profesionally.
My new Nissin flash was my first ever Canon DSLR compatible flash. OMG! You just put it on the hotshoe and take photos. No more mucking around with power settings and taking half a dozen shots to get things dialled in correctly. Who'd have thought flash photography could be so easy. Therefore, my suggestion would be to buy a flash that's compatible with Canon's E-TTL and E-TTLii metering modes. Then work out if you need high speed synch (a lot of people say it is unnecessary). Then look at the power of the flash (bearing in mind that manufacturers are creative about how this is measured - although the Canon 430EXii is regarded as more powerful than advertised). Other considerations include speed to refresh, AF assist light, master / slave mode, strobe mode and the amount of manual control you want. Then you have to worry about long term compatability of third party flashes with the Canon system. (Although many now have the ability to update firmware via USB).
If you see it as a long-term investment, the Canon 430EX ii represents good value. There's also talk of a 440EX-RT coming out later this year. This would be compatible with Canon's new radio trigger system and (hopefully) will be an awesome flash. But you'd need an extra accessory (an even more expensive flash or an ST-E3 flash controller) to get this to work properly with the new wireless system. I wouldn't wait for a hypothetical product that will be expensive to get working to its full capability.
Sorry about the long essay - slow day at work.