The BlackBerry 8520 goes on sale tomorrow via T-Mobile wireless stores and its retail partner Wal-Mart. If you're a budget shopper, I'd plan to buy at Wal-Mart, instead, as it'll save you about $80. Also, first impressions of the 8520.I met with Research In Motion representatives this morning. According to what they told me, T-Mobile is selling the BlackBerry 8520 at the price of $129.99 with a new two-year agreement. Wal-Mart is selling the same phone, with the same two-year requirement, for $48.88.

Does Wal-Mart enjoy undercutting its partners by a wide margin?

You may remember when T-Mobile first began selling the HTC G1 Android phone, Wal-Mart offered it at a substantial savings. This sparked a bit of controversy, as consumers were peeved that they could save a few Hamiltons if they had purchased the G1 at Wal-Mart instead of directly through T-Mobile.

This time around, at least you have fair warning. If you want to save a whopping $81.11 (or 62.4%), I'd highly recommend you shop at Wal-Mart rather than T-Mobile stores if you have the opportunity.

As for the hardware itself, the 8520 is small. Very easy on the hands, and highly pocketable. Though it supports all the enterprise services that its more advanced siblings support, the 8520 is clearly aimed at the prosumer/consumer market.

The biggest surprise, perhaps, is the optical mouse. I've used them on other handsets, and have not been impressed. This is the first optical mouse that I've encountered that I would say works well. It was very responsive, and is adjustable to match user input.

The 8520 is rimmed in a rubber coating, which makes it stick in the hand well. Media keys at the top of the phone make it easy to cycle through your music playlists.

As for the keyboard, it feels a bit tight for my larger hands, but those with smaller hands should have absolutely no problems with it.

Perhaps the biggest disappointment is the system software. RIM is relying on its tried-and-true 4.6.1 system software for the 8520, which means it doesn't have the latest design that is present on devices such as the Tour and Bold.

If you can manage to snag the 8520 at the budget-friendly Wal-Mart price of $48.88, it is a highly capable messaging device.