Personally I like Dell. I currently have two laptops I use Dell 15" Inspiron & a 17"Acer.. both are fine.
As far as the suggestion above to go with some extra performance blah blah blah to run a 2nd monitor... pleasezz... even my 4yr. Dell works great with a 2nd 23" monitor.
Between my partner & myself we have had at least 8-10 laptops in the past 2yrs. -> Toshiba, HP(x2), Dell (x5), Acer (x2), & Asus. I've preferred the Dell (but it's been close).
These days you can get a good laptop for f'n cheap!! A few years ago, 2GB Ram was very cool... now you're looking at 4GB being standard even in the cheaper models. A decent processor & 4GB Ram will be good to go for any poker you'll ever likely play (ie. on an Acer 4GB Ram with kind of a cheapo out-dated Intel Pentium processor I will run 5 poker sites
& can have over 20tables running, along with poker software (PT3, pokerprolabs), talking on Skype, checking out emails, watching a poker training vid., listening to a PokerPodcast & surfing the web all at the same time & never miss a beat..... what more could you need?). Unless you're needing your computer for some funky applications & are making movies or something, a standard model on the market these days will be uber good enough imo (although I'm fairly computer illiterate... yah.. even though we've owned so many of them.... we tend to give them out for gifts & then go grab another, lol). The two I'm currently using are 2 & 4yrs. old... both are fine for anything I'd ever want to do.
Also, I've shopped for laptops the past while at Walmart. They have great deals on there. Dell also runs some good specials at times & are cheap (service has been good for me with Dells also).
A few years ago I found that some laptops would have a bit of a heating issue (had cooling pads w fans for all of them & would also blast an external fan at my desk to keep them cooler).. but I haven't noticed that with any in the past 2yrs. (no longer bother with cooling pads but do keep the back ends of them elevated on a board/pad thingy I make for them, to allow for decent airflow under them.
My partner's favourites: 1st - Dell, 2nd - Toshiba, 3rd - Acer, (HP was actually last). Mine: 1st - Dell, 2nd - Acer (& they're f'n CHEAP!!!)