I personally like Toshibas, they seem to be really sturdy. I've seen some cheap-looking dells before. I'm not impressed with Dell as a company, they can advertise, sell decent computers, but they are bound to be cutting corners somewhere. Of course the same probably holds true for my Toshiba, but my Satellite looks nicer than anything Dell offers
Alienware Laptops offer the highest end componesnts for their laptops, and are more oriented towards gamers. Pretty heavy machines too. Not for the mobile user. Battery life I hear is pretty short on these laptops a well.
Dell Laptops offer some good values, but I have tried to do configurations with high-end componesnts and always end up getting a message that says "some componesnts in the configuration are not compatible." So then why was I given the option??? Dell offers different styles for people more concerned about weight (you usually sacrafice performance). I would also think that the lower the performance specs the more battery life.
Toshiba gives a great value, but they are heavy. This one here isn't even top of the line and it still ways a hefty 12lbs. There are some lower performing models that are lighter. Toshiba also has the best speakers built-in. NO OTHER LAPTOP SOUNDS THIS GOOD I PROMISE YOU! Very very good battery life. I can watch about 2 DVD movies no problem.
Sonys are popular because of their looks, but i am not a big fan of purple. Sony accesories, such as batteries, chargers etc. are the most expensive though. They also don't seem to be much of a value and I tend to think you are mostly paying for their name. I do think that Sony's have the best LCD displays though.
HP/Compaq - not a fan of HP's or Coimpaq, but I have seem some prices which definately rival Dell. Most of the compaq models are light-weight, while HP tends to have higher performing parts inside (depends on the model of course). I compared the displays once, and found that the HP is much crisper and has better color accuracy.
vprmatrix - the absolute worst speakers. Can barely hear the sound, plus they are on the front of the laptop so the sound waves are traveling at your chest, or at your legs (depending on how your sitting at your laptop). However their LCD display rivals Sony, and they even offer a version with widescreen, although I personally would like a full 15" display. The designs (even though coming from porsche) is really ugly IMO. Even though i work for best buy, I am not a big fan of this laptop. But the prices are competitive with Dell, and most likely you could talk a salesperson down if you brought in a Dell price (just don't tell them I told you, that you could).
Try to avoid mail-in rebates. I hate to say it, but they sometimes don't come back. Ones that are usually from the store you're buying from will come back within 2-4 weeks, and are not a problem. Dell and Toshiba are good with their rebates (friend owns a Dell Inspiron and tells me it's the best thing ever ALL the time - it's rather annoying especially when I have a better machine and paid less
). I have lost $60 to sony on a monitor so i won't comment on their rebates.
Get an extended warranty, although as a best buy employee, and do tend to think Service Plans have a bit more to offer at the same (or sometimes lower) price. If the warranty is somehow cheaper than the service plan than the obvious way to go is the extended warranty.