I'd look at the DiveRite Transpac II and Zeagle Ranger also.
It is nice, but if you're on a budget, you should consider that it isn't necessary. Most of my dives are executed without a computer... all you NEED to know is time, depth, pressure, and how to use a table. My computer flooded recently, and replacing it isn't a high priority for me.
It introduces additional task loading during emergencies, as you're going to have to both breathe and control buoyancy from that device simultaneously while sharing air and ascending. It can be done, but definately requires practice. Personally, I prefer a regular 2nd stage regulator as a backup. Keep it simple.
Yes, it's a good idea to have redundant gas supply. Yes, a pony can be a good idea. I use a "stage mounted" 40 cubic foot aluminium tank with an independant regulator on some dives, and I hardly notice it. I wouldn't say it's bulky at all... at least, not underwater.
40% to 60% of retail... depending on how good a haggler you are.
I think ianr33 makes a valid point. Walking into a store for advice and support when you have no intention of spending money there isn't a very good way to put yourself in their good graces.