I rent sometimes still from my shop just to be able to give a rental customer an honest opinion about how the ski feels on slope.
Other than that, I usually demo because the rental skis just won't cut it for high speed applications. Also, demo skis are usually better maintained. Rentals usually come back banged up and remain banged up (unless it requires an edge repair or base weld) but demos are kept in pretty good condition (most places usually sell them at the end of the season anyways).
When I first started back when i was like...4 or 5, my family rented. we only did 5-6 days a season, so it was much more economical. Besides, i didn't need high end equipment...neither did my parents. Nowadays, I want to try out the skis i intend on getting to see if they're worth getting...something you can't do with rentals.
Just make sure, defcon, that you get well fitting boots. A good fitting boot can mean the difference between sloppy and good technique. Also determines how long you stay on the slopes too.
I see you're from the bay area. For good ski sales, try REI in Saratoga or Any Mtn. If you want to know more about particular skis, head towards ski specialty shops such as Helm of Sun Valley. I've had lotsa luck with them. Tri-City in fremont has KILLER deals at the end of season. For starters, 3 seasons ago, they had the salomon performa prolink 9.0 XScream for $250 =) I couldn't find place that had them for under 400 come easter. Boot fitting, Helm of Sun Valley does a pretty good job.
Hope this helps =)