It depends what you are really going for. 17" is a mobile desktop replacement more than a laptop, meaning it's not really supposed to move, but if the need happens, it is possible.
My personal recommendation is to get a 15" screen for 3 reasons:
1- a 17", if used as a primary screen is a little small
2- 15" will get you a cheaper computer for the same specs
3- batteries will usually not last on such a big screen machine
And then add a 22" or 24" monitor as a dual screen at home, so if you're not moving it a lot, you got a good wide screen to use, and when you do need to move it, you got a standard sized/weight laptop that's easy to carry.
On a side note, I was checking Lenovo.ca right now, and they have huge sales on t410 and t510 (one if their highest series laptop that include a roll-cage, spill-proof keyboard, hard drive airbag protection, really worth it). If you end up using the laptop as a desktop replacement and think a dual monitor is a good idea, i highly recommend that series to you; it's what I got, and by experience in both consumer and professional products (from HP G60 to HP Elitebooks, I can tell you it's the best built machine I've seen to this day).
edit1 : I'll add a picture of two of my workstation at home, will get you an idea.
edit2 : the pics
full workstation
On the left is my media desktop pc, on the right my work laptop.
the dual screen with laptop I was talking to you about, added with a 24" samsung P2310.
I got the advanced minidock that comes with an extra charger, so when i come home i just plug it in, charges and goes to full desktop automatically, when i leave i press the eject button and i'm running on my laptop. I can even add an extra screen (for a total of 3) by VGA. Of course, adding a mouse and a keyboard makes you even more comfortable.
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for the record, if you do chose to go with a T series, you also have switchable graphics, so you have the motherboard integrated Intel graphic card, and the more powerful one (the new T series come with a nvidia GPU). So if you want more battery life, you run the intel one since it takes less energy, when you want to play or are at home on multiple screen, you run the Nvidia one. My battery (9 cell) goes up to 10 hours with the intel one when i am on the road.