Yahoo's option data has some problems. It often includes two series within the same chain without having any way of identifying the difference between the two besides the symbol chain which most people have no idea how to read. For those who are interested, I think that the CBOE has a guide somewhere to all the letters and how they distinguish between quarterlies and the regular series. You do want to know what you are trading before you trade. Otherwise, you may think that your options are about to expire when they actually have time left until the end of the calendar month. Better brokers such as TOS have their options chains set up to do this properly already. Clarity always helps with good decision making.
I have also found it annoying that Yahoo does not include index option data for SPX, NDX etc., which frankly are among the most actively traded options. It would be nice to check them on Yahoo. Hopefully someone over there is paying attention to this thread and can make the necessary changes!
As far as problems with Yahoo go, the delay in quotations is there, but it is among the least of the problems. Although options fluctuate in price throughout the day more than most people think (even when the underlying and the VIX are relatively quiet) , the delayed quotes will still give you a ballpark idea of what the prices should be. Most people should be wary of the quotes and double check using a reputable broker before making calculations and seriously investigating trades.
On a cautionary note, I also recommend that people check the prices for at least a couple of days on a regular basis (every 2-3 hours) to get a really good feel for what the prices should be and how they fluctuate before you initiate trades. To give you an idea of what I mean, I have seen an SPX iron condor midpoint prices (for more than a month away) vary by $0.50 or more during a single day when the SPX was basically doing zip all. Theoretically, no move, or even +/- 3 points should not change the net values for a month out more than five or ten cents. If you don't check ahead, you won't know this. This is especially important when you are doing multiple legged positions since there are several bid-ask spreads to account for. If the spreads happen to be poor at the moment, don't trade. You're just asking people to to take your money if you do that.
On another note, historical option data is available elsewhere, but good quality historical data is hard to find, and the amount of data is quite large. It will probably cost you money and overwhelm you with information. I think that it is better to monitor the data live for a number of days and use the historical IV versus current IV to make some estimates. You should also be aware that just because the IV is high doesn't mean that it will come down right away or vice versa. Back testing with options is tricky at the best of times! Predicting the future is even more difficult!