If you can get over the start-up cost of kegging, you will NEVER regret it! Almost everone that has made the switch wishes they had done it sooner.
Most homebrewers use corny kegs because there aren't really any other options. Commercial beer kegs (7.5 or 15 gal) are VERY expensive to obtain (assuming you do it legally), and are a pain to clean because there is no way to open them up and get an arm or brush inside them.
The going price for corny kegs in good shape is about $25 - $30. Princess Auto actually brought in a couple hundred of them at $25. I picked up a couple that were practically new. But you are correct -- they are no longer used by Coke and Pepsi, so when they sell off their stock of them, the price is going to skyrocket. Luckily, you can still find them if you hunt around a bit (watch the Buy and Sell in Calgary, plus eBay.ca).
The other nice thing about corny kegs over beer kegs is that you can get a couple inside a bar fridge or as many as four inside a regular fridge (I have seen pictures of six inside an over-sized fridge!). With beer kegs, the number is only one per fridge. If you follow the Buy and Sell or kijiji there is often someone giving away a free fridge, if cost is an issue.
I think most brewers force carbonate their beer with CO2 pressure. It carbs more quickly and does not produce additional sediment like priming with sugar, so your beer comes out a bit clearer at first. Personally, I see NO advantages to priming with sugar, other than reduced CO2 use.
If you do intend to keg, there is another great advantage -- the secondary fermentor becomes largely unneeded (except for things like fruit beers requiring a true second fermentation). So that means not only do you save on washing bottles, but HALF the fermentors, too!
Hope that helps.
Darren