SL is the wanna-be junkline, and it comes close to junk. The new manufacturing clones may however be slightly better as technology is rapidly improving.
You need to check out their displays, however, in your face, though. The older SL series with the Core 2 Duo processors had used really crappy screens which will not display text or images as well, even at 1:1 ratios compared to other supposedly lesser-quality laptops. Acer has had better LCD's than the SL line, if you'd ask me.
I agree with HiME. There are a lot of differences between their elite lines and the cheaper (mid-range garbage). For example, the older SL series only has an express card slot where the same T series that came out will have the both the express card and PC card slot functionalities, concerning expansion add-ons.
You gotta remember, you're not dealing with IBM anymore, you're dealin' with Lenovo. So if you're not paying for the top quality stuff, you might as well opt for another company's line if you don't got the cash for the T series.
The i3, you will notice nothing/very little compared to the i5 if you're not running more intense apps. Like the i5 vs. i7 on laptops, you will notice nothing if you're just an i-surfer or word processor go'er, music listener, etc. Intel integrated graphics are all junk compared to ATI and nVidia graphics solutions. Supposedly you may get better battery life with Intel graphics, but if you're an avg. user, it won't make a diff. Get a 7200rpm hard drive, 'cuz you will notice lag, even on a SATA300 interface, plus it will feel more like desktop-speedy with a 7200rpm drive.
ATI and nVidia solutions are better if you're gonna do photoshop stuff. It will be smoother and less choppy v.s. Intel graphics. i5 chip will make photoshop faster in crunching bits and larger works.
720 and 1080 is fine on external display(s) over HDMI, but I would not expect too many bells and whistles from this laptop you're looking into. If you really wanted to fork over 500-600 bucks for a laptop and have really good video quality, you might as well get a used laptop with a GTX260 graphics card with an LED 720/1080 display.
And I don't know what the hell Lenovo is doing, but for what the specs are upon preconfiguration, some of them come loaded with bloatware and useless software packages that slowdown overall system performance. So out of the box, possibly plan for a clean wipe with oem OS.