Good for you! Anything that gets you riding is fantastic. You'll lose some weight, reduce your chlorestorol, decrease blood pressure, live longer. You'll be more inclined to try your own maintenance (instead of fearing you'll damage a $700 bike). That will save you a lot of money and make you more comfortable working on an expensive bike if you ever get one. You'll also be more inclined to ride it places where you have to lock it up. Same principle: you might be afraid of losing a $700 bike. Getting experience with lock-up strategies will make you more comfortable with an expensive bike (if you ever choose to get one).

The only downside I see to a discount-store bike is: without significant care in the assembly (reassembly of factory assembled components) these bikes can be unreliable. Bearings may fail soon due to overtightened, insufficiently greased axles and bottom bracket. Tires may flat frequently due to sharp edges inside the rim. Some of the hybrid/comfort bikes come with 20-24 spoke wheels which I've seen spokes come loose after 1000 miles. That leads to wheel failure unless the rider is checking for and retentioning loose spokes.

Things like that could lead a new rider to have a negative experience, deciding bike riding isn't for them. But, with a little "sweat equity" they can have a very positive experience for 1/3 the money.

I did much the same thing with a Mongoose Paver from Walmart. $120, but I got it for $70 because it was damaged in transit. It got me into riding. I "moved up" to a Walmart Avenue, then Target Trailway (both much the same bike, subtle differences). Ended up picking up a used Specialized Sequoia ($800 road bike when new). And, I picked up a broken Dahon folding bike, rebuilding it, converting the rear derailer to a 7-speed internal-gear hub (lacing a new rim to the new hub, with custom length spokes! Wow, that was a learning experience).

All roads lead to Rome. This site isn't too intolerant of our kind. But, there are a few riders everywhere who think it's not possible to have a good experience with a "Walmart bike." If you find yourself stifled by such, there is a forum specific to people who ride these bikes. www.bigboxbikes.com (It suffers a little from the opposite problem: ridiculing people who spend a lot on a bike. It's good to remain exposed to the larger world of non-Walmart riders, find a balance, etc.).